HpxNDMap

class gammapy.maps.HpxNDMap(geom, data=None, dtype='float32', meta=None, unit='')

Bases: gammapy.maps.hpx.core.HpxMap

HEALPix map with any number of non-spatial dimensions.

This class uses an N+1D numpy array to represent the sequence of HEALPix image planes. Following the convention of WCS-based maps this class uses a column-wise ordering for the data array with the spatial dimension being tied to the last index of the array.

Parameters

geomHpxGeom

HEALPix geometry object.

datandarray

HEALPix data array. If None, then an empty array will be allocated.

metadict

Dictionary to store metadata.

unitstr or Unit

The map unit.

Attributes Summary

data	Data array as a ndarray object.
geom	Map geometry as a Geom object.
is_mask	Whether map is a mask with boolean data type.
meta	Map metadata as a dict.
quantity	Map data as a Quantity object.
tag
unit	Map unit as an Unit object.

Methods Summary

coadd(map_in[, weights])	Add the contents of map_in to this map.
convolve(kernel[, convolution_method])	Convolve map with a WCS kernel.
convolve_full(kernel)	Convolve map with a symmetrical WCS kernel.
convolve_wcs(kernel, **kwargs)	Convolve map with a WCS kernel.
copy(**kwargs)	Copy map instance and overwrite given attributes, except for geometry.
create([nside, binsz, nest, map_type, ...])	Factory method to create an empty HEALPix map.
crop(crop_width)	Crop the spatial dimensions of the map.
cumsum(axis_name)	Compute cumulative sum along a given axis.
cutout(position, width, *args, **kwargs)	Create a cutout around a given position.
downsample(factor[, preserve_counts, axis_name])	Downsample the spatial dimension by a given factor.
fill_by_coord(coords[, weights])	Fill pixels at coords with given weights.
fill_by_idx(idx[, weights])	Fill pixels at idx with given weights.
fill_by_pix(pix[, weights])	Fill pixels at pix with given weights.
fill_events(events[, weights])	Fill the map from an EventList object.
from_geom(geom[, meta, data, unit, dtype])	Generate an empty map from a Geom instance.
from_hdu(hdu[, hdu_bands, format, colname])	Make a HpxNDMap object from a FITS HDU.
from_hdulist(hdu_list[, hdu, hdu_bands, ...])	Make a HpxMap object from a FITS HDUList.
from_stack(maps[, axis, axis_name])	Create Map from a list of images and a non-spatial axis.
from_wcs_tiles(wcs_tiles[, nest])	Create HEALPix map from WCS tiles.
get_by_coord(coords[, fill_value])	Return map values at the given map coordinates.
get_by_idx(idx)	Return map values at the given pixel indices.
get_by_pix(pix[, fill_value])	Return map values at the given pixel coordinates.
get_image_by_coord(coords)	Return spatial map at the given axis coordinates.
get_image_by_idx(idx)	Return spatial map at the given axis pixel indices.
get_image_by_pix(pix)	Return spatial map at the given axis pixel coordinates
get_spectrum([region, func, weights])	Extract spectrum in a given region.
integral(axis_name, coords, **kwargs)	Compute integral along a given axis.
interp_by_coord(coords[, method, fill_value])	Interpolate map values at the given map coordinates.
interp_by_pix(pix[, method, fill_value])	Interpolate map values at the given pixel coordinates.
interp_to_geom(geom[, preserve_counts, ...])	Interpolate map to input geometry.
is_allclose(other[, rtol_axes, atol_axes])	Compare two Maps for close equivalency.
iter_by_axis(axis_name[, keepdims])	Iterate over a given axis.
iter_by_image([keepdims])	Iterate over image planes of a map.
iter_by_image_data()	Iterate over image planes of the map.
mask_nearest_position(position)	Given a sky coordinate return nearest valid position in the mask.
normalize([axis_name])	Normalise data in place along a given axis.
pad(pad_width[, axis_name, mode, cval, method])	Pad the spatial dimensions of the map.
plot([method, ax, normalize, proj, ...])	Quickplot method.
plot_grid([figsize, ncols])	Plot map as a grid of subplots for non-spatial axes.
plot_interactive([rc_params])	Plot map with interactive widgets to explore the non-spatial axes.
plot_mask([method, ax, proj, oversample, ...])	Plot the mask as a shaded area.
read(filename[, hdu, hdu_bands, map_type, ...])	Read a map from a FITS file.
reduce(axis_name[, func, keepdims, weights])	Reduce map over a single non-spatial axis.
reduce_over_axes([func, keepdims, ...])	Reduce map over non-spatial axes.
rename_axes(names, new_names)	Rename the Map axes.
reproject_to_geom(geom[, preserve_counts, ...])	Reproject map to input geometry.
resample(geom[, weights, preserve_counts])	Resample pixels to geom with given weights.
resample_axis(axis[, weights, ufunc])	Resample map to a new axis by grouping and reducing smaller bins by a given function ufunc.
sample_coord(n_events[, random_state])	Sample position and energy of events.
set_by_coord(coords, vals)	Set pixels at coords with given vals.
set_by_idx(idx, vals)	Set pixels at idx with given vals.
set_by_pix(pix, vals)	Set pixels at pix with given vals.
slice_by_idx(slices)	Slice sub map from map object.
smooth(width[, kernel])	Smooth the map.
split_by_axis(axis_name)	Split a Map along an axis into multiple maps.
stack(other[, weights, nan_to_num])	Stack cutout into map.
sum_over_axes([axes_names, keepdims, weights])	Sum map values over all non-spatial axes.
to_cube(axes)	Append non-spatial axes to create a higher-dimensional Map.
to_hdu([hdu, hdu_bands, sparse, format])	Make a FITS HDU with input data.
to_hdulist([hdu, hdu_bands, sparse, format])	Convert to HDUList.
to_nside(nside[, preserve_counts])	Upsample or downsample the map to a given nside.
to_region_nd_map(region[, func, weights, method])	Get region ND map in a given region.
to_swapped()	Return a new map with the opposite scheme (ring or nested).
to_unit(unit)	Convert map to a different unit.
to_wcs([sum_bands, normalize, proj, ...])	Make a WCS object and convert HEALPix data into WCS projection.
to_wcs_tiles([nside_tiles, margin, method, ...])	Convert HpxNDMap to a list of WCS tiles.
upsample(factor[, order, preserve_counts, ...])	Upsample the spatial dimension by a given factor.
write(filename[, overwrite])	Write to a FITS file.

Attributes Documentation

data

Data array as a ndarray object.

geom

Map geometry as a Geom object.

is_mask

Whether map is a mask with boolean data type.

meta

Map metadata as a dict.

quantity

Map data as a Quantity object.

tag = 'map'

unit

Map unit as an Unit object.

Methods Documentation

coadd(map_in, weights=None)

Add the contents of map_in to this map.

This method can be used to combine maps containing integral quantities (e.g. counts) or differential quantities if the maps have the same binning.

Parameters

map_inMap

Map to add.

weights: `Map` or `~numpy.ndarray`

The weight factors while adding. Default is None.

convolve(kernel, convolution_method='wcs-tan', **kwargs)

Convolve map with a WCS kernel.

Project the map into a WCS geometry, convolve with a WCS kernel and project back into the initial HEALPix geometry.

If the kernel is two-dimensional, it is applied to all image planes likewise. If the kernel is higher dimensional it must match the map in the number of dimensions and the corresponding kernel is selected for every image plane.

Parameters

kernelPSFKernel

Convolution kernel. The pixel size must be upsampled by a factor 2 or bigger with respect to the input map to prevent artifacts in the projection.

convolution_method{“wcs-tan”, “”}, optional

Convolution method. If “wcs-tan”, project on WCS geometry and convolve with WCS kernel. See convolve_wcs. If “”, convolve map with a symmetrical WCS kernel. See convolve_full. Default is “wcs-tan”.

**kwargsdict

Keyword arguments passed to convolve.

Returns

mapHpxNDMap

Convolved map.

convolve_full(kernel)

Convolve map with a symmetrical WCS kernel.

Extract the radial profile of the kernel (assuming radial symmetry) and convolve via smoothing. Since no projection is applied, this is suited for full-sky and large maps.

If the kernel is two-dimensional, it is applied to all image planes likewise. If the kernel is higher dimensional it must match the map in the number of dimensions and the corresponding kernel is selected for every image plane.

Parameters

kernelPSFKernel

Convolution kernel. The pixel size must be upsampled by a factor 2 or bigger with respect to the input map to prevent artifacts in the projection.

Returns

mapHpxNDMap

Convolved map.

convolve_wcs(kernel, **kwargs)

Convolve map with a WCS kernel.

Project the map into a WCS geometry, convolve with a WCS kernel and project back into the initial HEALPix geometry.

If the kernel is two-dimensional, it is applied to all image planes likewise. If the kernel is higher dimensional should either match the map in the number of dimensions or the map must be an image (no non-spatial axes). In that case, the corresponding kernel is selected and applied to every image plane or to the single input image respectively.

Parameters

kernelPSFKernel

Convolution kernel. The pixel size must be upsampled by a factor 2 or bigger with respect to the input map to prevent artifacts in the projection.

**kwargsdict

Keyword arguments passed to convolve.

Returns

mapHpxNDMap

Convolved map.

copy(**kwargs)

Copy map instance and overwrite given attributes, except for geometry.

Parameters

**kwargsdict, optional

Keyword arguments to overwrite in the map constructor.

Returns

copyMap

Copied Map.

classmethod create(nside=None, binsz=None, nest=True, map_type='hpx', frame='icrs', data=None, skydir=None, width=None, dtype='float32', region=None, axes=None, meta=None, unit='')

Factory method to create an empty HEALPix map.

Parameters

nsideint or ndarray, optional

HEALPix NSIDE parameter. This parameter sets the size of the spatial pixels in the map. Default is None.

binszfloat or ndarray, optional

Approximate pixel size in degrees. An NSIDE will be chosen that corresponds to a pixel size closest to this value. This option is superseded by nside. Default is None.

nestbool, optional

Indexing scheme. If True, “NESTED” scheme. If False, “RING” scheme. Default is True.

map_type{‘hpx’, ‘hpx-sparse’}, optional

Map type. Selects the class that will be used to instantiate the map. Default is “hpx”.

frame{“icrs”, “galactic”}, optional

Coordinate system, either Galactic (“galactic”) or Equatorial (“icrs”). Default is “icrs”.

datandarray, optional

Data array. Default is None.

skydirtuple or SkyCoord, optional

Sky position of map center. Can be either a SkyCoord object or a tuple of longitude and latitude in deg in the coordinate system of the map. Default is None.

widthfloat, optional

Diameter of the map in degrees. If None then an all-sky geometry will be created. Default is None.

dtypestr, optional

Data type. Default is “float32”.

regionstr, optional

HEALPix region string. Default is None.

axeslist, optional

List of MapAxis objects for each non-spatial dimension. Default is None.

metadict, optional

Dictionary to store the metadata. Default is None.

unitstr or Unit, optional

The map unit. Default is “”.

Returns

mapHpxMap

A HEALPix map object.

crop(crop_width)

Crop the spatial dimensions of the map.

Parameters

crop_width{sequence, array_like, int}

Number of pixels cropped from the edges of each axis. Defined analogously to pad_with from numpy.pad.

Returns

mapMap

Cropped map.

cumsum(axis_name)

Compute cumulative sum along a given axis.

Parameters

axis_namestr

Along which axis to sum.

Returns

cumsumMap

Map with cumulative sum.

cutout(position, width, *args, **kwargs)

Create a cutout around a given position.

Parameters

positionSkyCoord

Center position of the cutout region.

widthAngle or Quantity

Diameter of the circular cutout region.

Returns

cutoutHpxNDMap

Cutout map.

downsample(factor, preserve_counts=True, axis_name=None)

Downsample the spatial dimension by a given factor.

Parameters

factorint

Downsampling factor.

preserve_countsbool, optional

Preserve the integral over each bin. This should be set to True if the map is an integral quantity (e.g. counts) and False if the map is a differential quantity (e.g. intensity). Default is True.

axis_namestr, optional

Which axis to downsample. By default, spatial axes are downsampled. Default is None.

Returns

mapMap

Downsampled map.

fill_by_coord(coords, weights=None)

Fill pixels at coords with given weights.

Parameters

coordstuple or MapCoord

Coordinate arrays for each dimension of the map. Tuple should be ordered as (lon, lat, x_0, …, x_n) where x_i are coordinates for non-spatial dimensions of the map.

weightsndarray, optional

Weights vector. If None, weights are set to 1. Default is None.

fill_by_idx(idx, weights=None)

Fill pixels at idx with given weights.

Parameters

idxtuple

Tuple of pixel index arrays for each dimension of the map. Tuple should be ordered as (I_lon, I_lat, I_0, …, I_n) for WCS maps and (I_hpx, I_0, …, I_n) for HEALPix maps.

weightsndarray, optional

Weights vector. If None, weights are set to 1. Default is None.

fill_by_pix(pix, weights=None)

Fill pixels at pix with given weights.

Parameters

pixtuple

Tuple of pixel index arrays for each dimension of the map. Tuple should be ordered as (I_lon, I_lat, I_0, …, I_n) for WCS maps and (I_hpx, I_0, …, I_n) for HEALPix maps. Pixel indices can be either float or integer type. Float indices will be rounded to the nearest integer.

weightsndarray, optional

Weights vector. If None, weights are set to 1. Default is None.

fill_events(events, weights=None)

Fill the map from an EventList object.

Parameters

eventsEventList

Events to fill in the map with.

weightsndarray, optional

Weights vector. The weights vector must be of the same length as the events column length. If None, weights are set to 1. Default is None.

static from_geom(geom, meta=None, data=None, unit='', dtype='float32')

Generate an empty map from a Geom instance.

Parameters

geomGeom

Map geometry.

metadict, optional

Dictionary to store metadata. Default is None.

datanumpy.ndarray, optional

Data array. Default is None.

unitstr or Unit

Data unit.

dtypestr, optional

Data type. Default is ‘float32’.

Returns

map_outMap

Map object.

classmethod from_hdu(hdu, hdu_bands=None, format=None, colname=None)

Make a HpxNDMap object from a FITS HDU.

Parameters

hduBinTableHDU

The FITS HDU.

hdu_bandsBinTableHDU, optional

The BANDS table HDU. Default is None.

formatstr, optional

FITS convention. Default is None. If None the format is guessed. The following formats are supported:

• “gadf”

• “fgst-ccube”

• “fgst-ltcube”

• “fgst-bexpcube”

• “fgst-srcmap”

• “fgst-template”

• “fgst-srcmap-sparse”

• “galprop”

• “galprop2”

colnamestr, optional

Data column name to be used for the HEALPix map. Default is None.

Returns

mapHpxMap

HEALPix map.

classmethod from_hdulist(hdu_list, hdu=None, hdu_bands=None, format=None, colname=None)

Make a HpxMap object from a FITS HDUList.

Parameters

hdu_listHDUList

HDU list containing HDUs for map data and bands.

hdustr, optional

Name or index of the HDU with the map data. If None then the method will try to load map data from the first BinTableHDU in the file. Default is None.

hdu_bandsstr, optional

Name or index of the HDU with the BANDS table. Default is None.

formatstr, optional

FITS format convention. By default, files will be written to the gamma-astro-data-formats (GADF) format. This option can be used to write files that are compliant with format conventions required by specific software (e.g. the Fermi Science Tools). The following formats are supported:

• “gadf” (default)

• “fgst-ccube”

• “fgst-ltcube”

• “fgst-bexpcube”

• “fgst-srcmap”

• “fgst-template”

• “fgst-srcmap-sparse”

• “galprop”

• “galprop2”

Returns

hpx_mapHpxMap

Map object.

classmethod from_stack(maps, axis=None, axis_name=None)

Create Map from a list of images and a non-spatial axis.

The image geometries must be aligned, except for the axis that is stacked.

Parameters

mapslist of Map objects

List of maps.

axisMapAxis, optional

If a MapAxis is provided the maps are stacked along the last data axis and the new axis is introduced. Default is None.

axis_namestr, optional

If an axis name is as string the given the maps are stacked along the given axis name.

Returns

mapMap

Map with additional non-spatial axis.

classmethod from_wcs_tiles(wcs_tiles, nest=True)

Create HEALPix map from WCS tiles.

Parameters

wcs_tileslist of WcsNDMap

WCS map tiles.

nestbool, optional

Indexing scheme. If True, “NESTED” scheme. If False, “RING” scheme. Default is True.

Returns

hpx_mapHpxNDMap

HEALPix map.

get_by_coord(coords, fill_value=nan)

Return map values at the given map coordinates.

Parameters

coordstuple or MapCoord

Coordinate arrays for each dimension of the map. Tuple should be ordered as (lon, lat, x_0, …, x_n) where x_i are coordinates for non-spatial dimensions of the map.

fill_valuefloat

Value which is returned if the position is outside the projection footprint. Default is numpy.nan.

Returns

valsndarray

Values of pixels in the map. numpy.nan is used to flag coordinates outside the map.

get_by_idx(idx)

Return map values at the given pixel indices.

Parameters

idxtuple

Tuple of pixel index arrays for each dimension of the map. Tuple should be ordered as (I_lon, I_lat, I_0, …, I_n) for WCS maps and (I_hpx, I_0, …, I_n) for HEALPix maps.

Returns

valsndarray

Array of pixel values. numpy.nan is used to flag coordinates outside the map.

get_by_pix(pix, fill_value=nan)

Return map values at the given pixel coordinates.

Parameters

pixtuple

Tuple of pixel index arrays for each dimension of the map. Tuple should be ordered as (I_lon, I_lat, I_0, …, I_n) for WCS maps and (I_hpx, I_0, …, I_n) for HEALPix maps. Pixel indices can be either float or integer type.

fill_valuefloat

Value which is returned if the position is outside the projection footprint. Default is numpy.nan.

Returns

valsndarray

Array of pixel values. numpy.nan is used to flag coordinates outside the map.

get_image_by_coord(coords)

Return spatial map at the given axis coordinates.

Parameters

coordstuple or dict

Tuple should be ordered as (x_0, …, x_n) where x_i are coordinates for non-spatial dimensions of the map. Dictionary should specify the axis names of the non-spatial axes such as {‘axes0’: x_0, …, ‘axesn’: x_n}.

Returns

map_outMap

Map with spatial dimensions only.

See also

get_image_by_idx, get_image_by_pix.

Examples

import numpy as np
from gammapy.maps import Map, MapAxis
from astropy.coordinates import SkyCoord
from astropy import units as u

# Define map axes
energy_axis = MapAxis.from_edges(
    np.logspace(-1., 1., 4), unit='TeV', name='energy',
)

time_axis = MapAxis.from_edges(
    np.linspace(0., 10, 20), unit='h', name='time',
)

# Define map center
skydir = SkyCoord(0, 0, frame='galactic', unit='deg')

# Create map
m_wcs = Map.create(
    map_type='wcs',
    binsz=0.02,
    skydir=skydir,
    width=10.0,
    axes=[energy_axis, time_axis],
)

# Get image by coord tuple
image = m_wcs.get_image_by_coord(('500 GeV', '1 h'))

# Get image by coord dict with strings
image = m_wcs.get_image_by_coord({'energy': '500 GeV', 'time': '1 h'})

# Get image by coord dict with quantities
image = m_wcs.get_image_by_coord({'energy': 0.5 * u.TeV, 'time': 1 * u.h})

get_image_by_idx(idx)

Return spatial map at the given axis pixel indices.

Parameters

idxtuple

Tuple of scalar indices for each non-spatial dimension of the map. Tuple should be ordered as (I_0, …, I_n).

Returns

map_outMap

Map with spatial dimensions only.

See also

get_image_by_coord, get_image_by_pix.

get_image_by_pix(pix)

Return spatial map at the given axis pixel coordinates

Parameters

pixtuple

Tuple of scalar pixel coordinates for each non-spatial dimension of the map. Tuple should be ordered as (I_0, …, I_n). Pixel coordinates can be either float or integer type.

Returns

map_outMap

Map with spatial dimensions only.

See also

get_image_by_coord, get_image_by_idx.

get_spectrum(region=None, func=<function nansum>, weights=None)

Extract spectrum in a given region.

The spectrum can be computed by summing (or, more generally, applying func) along the spatial axes in each energy bin. This occurs only inside the region, which by default is assumed to be the whole spatial extension of the map.

Parameters

region: `~regions.Region`, optional

Region to extract the spectrum from. Pixel or sky regions are accepted. Default is None.

funcnumpy.func, optional

Function to reduce the data. Default is nansum. For a boolean Map, use numpy.any or numpy.all. Default is numpy.nansum.

weightsWcsNDMap, optional

Array to be used as weights. The geometry must be equivalent. Default is None.

Returns

spectrumRegionNDMap

Spectrum in the given region.

integral(axis_name, coords, **kwargs)

Compute integral along a given axis.

This method uses interpolation of the cumulative sum.

Parameters

axis_namestr

Along which axis to integrate.

coordsdict or MapCoord

Map coordinates.

**kwargsdict, optional

Keyword arguments passed to Map.interp_by_coord.

Returns

arrayQuantity

2D array with axes offset.

interp_by_coord(coords, method='linear', fill_value=None)

Interpolate map values at the given map coordinates.

Parameters

coordstuple or MapCoord

Coordinate arrays for each dimension of the map. Tuple should be ordered as (lon, lat, x_0, …, x_n) where x_i are coordinates for non-spatial dimensions of the map.

method{“linear”, “nearest”}

Method to interpolate data values. Default is “linear”.

fill_valuefloat, optional

The value to use for points outside the interpolation domain. If None, values outside the domain are extrapolated. Default is None.

Returns

valsndarray

Interpolated pixel values.

interp_by_pix(pix, method=None, fill_value=None)

Interpolate map values at the given pixel coordinates.

interp_to_geom(geom, preserve_counts=False, fill_value=0, **kwargs)

Interpolate map to input geometry.

Parameters

geomGeom

Target Map geometry.

preserve_countsbool, optional

Preserve the integral over each bin. This should be true if the map is an integral quantity (e.g. counts) and false if the map is a differential quantity (e.g. intensity). Default is False.

fill_valuefloat, optional

The value to use for points outside the interpolation domain. Default is 0.

**kwargsdict, optional

Keyword arguments passed to Map.interp_by_coord.

Returns

interp_mapMap

Interpolated Map.

is_allclose(other, rtol_axes=0.001, atol_axes=1e-06, **kwargs)

Compare two Maps for close equivalency.

Parameters

othergammapy.maps.Map

The Map to compare against.

rtol_axesfloat, optional

Relative tolerance for the axes’ comparison. Default is 1e-3.

atol_axesfloat, optional

Absolute tolerance for the axes’ comparison. Default is 1e-6.

**kwargsdict, optional

Keywords passed to allclose.

Returns

is_allclosebool

Whether the Map is all close.

iter_by_axis(axis_name, keepdims=False)

Iterate over a given axis.

Yields

mapMap

Map iteration.

See also

iter_by_image

iterate by image returning a map.

iter_by_image(keepdims=False)

Iterate over image planes of a map.

Parameters

keepdimsbool, optional

Keep dimensions. Default is False.

Yields

mapMap

Map iteration.

See also

iter_by_image_data

iterate by image returning data and index.

iter_by_image_data()

Iterate over image planes of the map.

The image plane index is in data order, so that the data array can be indexed directly.

Yields

(data, idx)tuple

Where data is a numpy.ndarray view of the image plane data, and idx is a tuple of int, the index of the image plane.

See also

iter_by_image

iterate by image returning a map.

mask_nearest_position(position)

Given a sky coordinate return nearest valid position in the mask.

If the mask contains additional axes, the mask is reduced over those axes.

Parameters

positionSkyCoord

Test position.

Returns

positionSkyCoord

The nearest position in the mask.

normalize(axis_name=None)

Normalise data in place along a given axis.

Parameters

axis_namestr, optional

Along which axis to normalise.

pad(pad_width, axis_name=None, mode='constant', cval=0, method='linear')

Pad the spatial dimensions of the map.

Parameters

pad_width{sequence, array_like, int}

Number of pixels padded to the edges of each axis.

axis_namestr, optional

Which axis to downsample. By default, spatial axes are padded. Default is None.

mode{‘constant’, ‘edge’, ‘interp’}

Padding mode. ‘edge’ pads with the closest edge value. ‘constant’ pads with a constant value. ‘interp’ pads with an extrapolated value. Default is ‘constant’.

cvalfloat, optional

Padding value when `mode`=’consant’. Default is 0.

Returns

mapMap

Padded map.

plot(method='raster', ax=None, normalize=False, proj='AIT', oversample=2, width_pix=1000, **kwargs)

Quickplot method.

This will generate a visualization of the map by converting to a rasterized WCS image (method=’raster’) or drawing polygons for each pixel (method=’poly’).

Parameters

method{‘raster’,’poly’}, optional

Method for mapping HEALPix pixels to a two-dimensional image. Can be set to ‘raster’ (rasterization to cartesian image plane) or ‘poly’ (explicit polygons for each pixel). WARNING: The ‘poly’ method is much slower than ‘raster’ and only suitable for maps with less than ~10k pixels. Default is “raster”.

projstring, optional

Any valid WCS projection type. Default is “AIT”.

oversamplefloat, optional

Oversampling factor for WCS map. This will be the approximate ratio of the width of a HPX pixel to a WCS pixel. If this parameter is None then the width will be set from width_pix. Default is 2.

width_pixint, optional

Width of the WCS geometry in pixels. The pixel size will be set to the number of pixels satisfying oversample or width_pix whichever is smaller. If this parameter is None then the width will be set from oversample. Default is 1000.

**kwargsdict

Keyword arguments passed to imshow.

Returns

axWCSAxes

WCS axes object.

plot_grid(figsize=None, ncols=3, **kwargs)

Plot map as a grid of subplots for non-spatial axes.

Parameters

figsizetuple of int, optional

Figsize to plot on. Default is None.

ncolsint, optional

Number of columns to plot. Default is 3.

**kwargsdict, optional

Keyword arguments passed to WcsNDMap.plot.

Returns

axesndarray of Axes

Axes grid.

plot_interactive(rc_params=None, **kwargs)

Plot map with interactive widgets to explore the non-spatial axes.

Parameters

rc_paramsdict, optional

Passed to matplotlib.rc_context(rc=rc_params) to style the plot. Default is None.

**kwargsdict, optional

Keyword arguments passed to WcsNDMap.plot.

Examples

You can try this out e.g. using a Fermi-LAT diffuse model cube with an energy axis:

from gammapy.maps import Map

m = Map.read("$GAMMAPY_DATA/fermi_3fhl/gll_iem_v06_cutout.fits")
m.plot_interactive(add_cbar=True, stretch="sqrt")

If you would like to adjust the figure size you can use the rc_params argument:

rc_params = {'figure.figsize': (12, 6), 'font.size': 12}
m.plot_interactive(rc_params=rc_params)

plot_mask(method='raster', ax=None, proj='AIT', oversample=2, width_pix=1000, **kwargs)

Plot the mask as a shaded area.

Parameters

method{‘raster’,’poly’}, optional

Method for mapping HEALPix pixels to a two-dimensional image. Can be set to ‘raster’ (rasterization to cartesian image plane) or ‘poly’ (explicit polygons for each pixel). WARNING: The ‘poly’ method is much slower than ‘raster’ and only suitable for maps with less than ~10k pixels. Default is “raster”.

projstring, optional

Any valid WCS projection type. Default is “AIT”.

oversamplefloat, optional

Oversampling factor for WCS map. This will be the approximate ratio of the width of a HPX pixel to a WCS pixel. If this parameter is None then the width will be set from width_pix. Default is 2.

width_pixint, optional

Width of the WCS geometry in pixels. The pixel size will be set to the number of pixels satisfying oversample or width_pix whichever is smaller. If this parameter is None then the width will be set from oversample. Default is 1000.

**kwargsdict

Keyword arguments passed to imshow.

Returns

axWCSAxes

WCS axis object.

static read(filename, hdu=None, hdu_bands=None, map_type='auto', format=None, colname=None)

Read a map from a FITS file.

Parameters

filenamestr or Path

Name of the FITS file.

hdustr, optional

Name or index of the HDU with the map data. Default is None.

hdu_bandsstr, optional

Name or index of the HDU with the BANDS table. If not defined this will be inferred from the FITS header of the map HDU. Default is None.

map_type{‘auto’, ‘wcs’, ‘wcs-sparse’, ‘hpx’, ‘hpx-sparse’, ‘region’}

Map type. Selects the class that will be used to instantiate the map. The map type should be consistent with the format of the input file. If map_type is ‘auto’ then an appropriate map type will be inferred from the input file. Default is ‘auto’.

colnamestr, optional

data column name to be used for HEALPix map.

Returns

map_outMap

Map object.

reduce(axis_name, func=<ufunc 'add'>, keepdims=False, weights=None)

Reduce map over a single non-spatial axis.

Parameters

axis_name: str

The name of the axis to reduce over.

funcufunc, optional

Function to use for reducing the data. Default is numpy.add.

keepdimsbool, optional

If this is set to true, the axes which are summed over are left in the map with a single bin. Default is False.

weightsMap

Weights to be applied. The map should have the same geometry as this one. Default is None.

Returns

map_outMap

Map with the given non-spatial axes reduced.

reduce_over_axes(func=<ufunc 'add'>, keepdims=False, axes_names=None, weights=None)

Reduce map over non-spatial axes.

Parameters

funcufunc, optional

Function to use for reducing the data. Default is numpy.add.

keepdimsbool, optional

If this is set to true, the axes which are summed over are left in the map with a single bin. Default is False.

axes_names: list, optional

Names of axis to reduce over. If None, all non-spatial axis will be reduced.

weightsMap, optional

Weights to be applied. The map should have the same geometry as this one. Default is None.

Returns

map_outMap

Map with non-spatial axes reduced.

rename_axes(names, new_names)

Rename the Map axes.

Parameters

namesstr or list of str

Names of the axes.

new_namesstr or list of str

New names of the axes. The list must be of the same length as names).

Returns

geomMap

Map with renamed axes.

reproject_to_geom(geom, preserve_counts=False, precision_factor=10)

Reproject map to input geometry.

Parameters

geomGeom

Target Map geometry.

preserve_countsbool, optional

Preserve the integral over each bin. This should be true if the map is an integral quantity (e.g. counts) and false if the map is a differential quantity (e.g. intensity). Default is False.

precision_factorint, optional

Minimal factor between the bin size of the output map and the oversampled base map. Used only for the oversampling method. Default is 10.

Returns

output_mapMap

Reprojected Map.

resample(geom, weights=None, preserve_counts=True)

Resample pixels to geom with given weights.

Parameters

geomGeom

Target Map geometry.

weightsndarray, optional

Weights vector. It must have same shape as the data of the map. If set to None, weights will be set to 1. Default is None.

preserve_countsbool, optional

Preserve the integral over each bin. This should be true if the map is an integral quantity (e.g. counts) and false if the map is a differential quantity (e.g. intensity). Default is True.

Returns

resampled_mapMap

Resampled map.

resample_axis(axis, weights=None, ufunc=<ufunc 'add'>)

Resample map to a new axis by grouping and reducing smaller bins by a given function ufunc.

By default, the map content are summed over the smaller bins. Other numpy.ufunc can be used, e.g. numpy.logical_and or numpy.logical_or.

Parameters

axisMapAxis

New map axis.

weightsMap, optional

Array to be used as weights. The spatial geometry must be equivalent to other and additional axes must be broadcastable. If set to None, weights will be set to 1. Default is None.

ufuncufunc

Universal function to use to resample the axis. Default is numpy.add.

Returns

mapMap

Map with resampled axis.

sample_coord(n_events, random_state=0)

Sample position and energy of events.

Parameters

n_eventsint

Number of events to sample.

random_state{int, ‘random-seed’, ‘global-rng’, RandomState}

Defines random number generator initialisation. Passed to get_random_state. Default is 0.

Returns

coordsMapCoord object.

Sequence of coordinates and energies of the sampled events.

set_by_coord(coords, vals)

Set pixels at coords with given vals.

Parameters

coordstuple or MapCoord

Coordinate arrays for each dimension of the map. Tuple should be ordered as (lon, lat, x_0, …, x_n) where x_i are coordinates for non-spatial dimensions of the map.

valsndarray

Values vector.

set_by_idx(idx, vals)

Set pixels at idx with given vals.

Parameters

idxtuple

Tuple of pixel index arrays for each dimension of the map. Tuple should be ordered as (I_lon, I_lat, I_0, …, I_n) for WCS maps and (I_hpx, I_0, …, I_n) for HEALPix maps.

valsndarray

Values vector.

set_by_pix(pix, vals)

Set pixels at pix with given vals.

Parameters

pixtuple

Tuple of pixel index arrays for each dimension of the map. Tuple should be ordered as (I_lon, I_lat, I_0, …, I_n) for WCS maps and (I_hpx, I_0, …, I_n) for HEALPix maps. Pixel indices can be either float or integer type. Float indices will be rounded to the nearest integer.

valsndarray

Values vector.

slice_by_idx(slices)

Slice sub map from map object.

Parameters

slicesdict

Dictionary of axes names and integers or slice object pairs. Contains one element for each non-spatial dimension. For integer indexing the corresponding axes is dropped from the map. Axes not specified in the dictionary are kept unchanged.

Returns

map_outMap

Sliced map object.

smooth(width, kernel='gauss')

Smooth the map.

Iterates over 2D image planes, processing one at a time.

Parameters

widthQuantity, str or float

Smoothing width given as quantity or float. If a float is given it is interpreted as smoothing width in pixels. If an (angular) quantity is given it is converted to pixels using nside2resol. It corresponds to the standard deviation in case of a Gaussian kernel, and the radius in case of a disk kernel.

kernel{‘gauss’, ‘disk’}, optional

Kernel shape. Default is “gauss”.

Returns

imageHpxNDMap

Smoothed image (a copy, the original object is unchanged).

split_by_axis(axis_name)

Split a Map along an axis into multiple maps.

Parameters

axis_namestr

Name of the axis to split.

Returns

mapslist

A list of Map.

stack(other, weights=None, nan_to_num=True)

Stack cutout into map.

Parameters

otherHpxNDMap

Other map to stack.

weightsHpxNDMap, optional

Array to be used as weights. The spatial geometry must be equivalent to other and additional axes must be broadcastable. Default is None.

nan_to_num: bool, optional

Non-finite values are replaced by zero if True. Default is True.

sum_over_axes(axes_names=None, keepdims=True, weights=None)

Sum map values over all non-spatial axes.

Parameters

axes_names: list of str

Names of the axis to reduce over. If None, all non-spatial axis will be summed over. Default is None.

keepdimsbool, optional

If this is set to true, the axes which are summed over are left in the map with a single bin. Default is True.

weightsMap, optional

Weights to be applied. The map should have the same geometry as this one. Default is None.

Returns

map_outMap

Map with non-spatial axes summed over.

to_cube(axes)

Append non-spatial axes to create a higher-dimensional Map.

This will result in a Map with a new geometry with N+M dimensions where N is the number of current dimensions and M is the number of axes in the list. The data is reshaped onto this new geometry.

Parameters

axeslist

Axes that will be appended to this Map. The axes should have only one bin.

Returns

mapWcsNDMap

New map.

to_hdu(hdu=None, hdu_bands=None, sparse=False, format=None)

Make a FITS HDU with input data.

Parameters

hdustr, optional

The HDU extension name. Default is None.

hdu_bandsstr, optional

The HDU extension name for BANDS table. Default is None.

sparsebool, optional

Set INDXSCHM to SPARSE and sparsify the map by only writing pixels with non-zero amplitude. Default is False.

format{‘fgst-ccube’, ‘fgst-template’, ‘gadf’, None}, optional

FITS format convention. If None this will be set to the default convention of the map. Default is None.

Returns

hdu_outBinTableHDU or ImageHDU

Output HDU containing map data.

to_hdulist(hdu='SKYMAP', hdu_bands=None, sparse=False, format='gadf')

Convert to HDUList.

Parameters

hdustr, optional

The HDU extension name. Default is “SKYMAP”.

hdu_bandsstr, optional

The HDU extension name for BANDS table. Default is None.

sparsebool, optional

Set INDXSCHM to SPARSE and sparsify the map by only writing pixels with non-zero amplitude. Default is False.

formatstr, optional

FITS format convention. By default, files will be written to the gamma-astro-data-formats (GADF) format. This option can be used to write files that are compliant with format conventions required by specific software (e.g. the Fermi Science Tools). The following formats are supported:

• “gadf” (default)

• “fgst-ccube”

• “fgst-ltcube”

• “fgst-bexpcube”

• “fgst-srcmap”

• “fgst-template”

• “fgst-srcmap-sparse”

• “galprop”

• “galprop2”

Returns

hdu_listHDUList

The FITS HDUList.

to_nside(nside, preserve_counts=True)

Upsample or downsample the map to a given nside.

Parameters

nsideint

HEALPix NSIDE parameter.

preserve_countsbool, optional

Preserve the integral over each bin. This should be true if the map is an integral quantity (e.g. counts) and false if the map is a differential quantity (e.g. intensity). Default is True.

Returns

geomHpxNDMap

HEALPix map with new NSIDE.

to_region_nd_map(region, func=<function nansum>, weights=None, method='nearest')

Get region ND map in a given region.

By default, the whole map region is considered.

Parameters

region: `~regions.Region` or `~astropy.coordinates.SkyCoord`

Region.

funcnumpy.func, optional

Function to reduce the data. Default is np.nansum. For boolean Map, use np.any or np.all.

weightsWcsNDMap, optional

Array to be used as weights. The geometry must be equivalent. Default is None.

method{“nearest”, “linear”}, optional

How to interpolate if a position is given. Default is “neraest”.

Returns

spectrumRegionNDMap

Spectrum in the given region.

to_swapped()

Return a new map with the opposite scheme (ring or nested).

Returns

mapHpxMap

Map object.

to_unit(unit)

Convert map to a different unit.

Parameters

unitstr or Unit

New unit.

Returns

mapMap

Map with new unit and converted data.

to_wcs(sum_bands=False, normalize=True, proj='AIT', oversample=2, width_pix=None, hpx2wcs=None, fill_nan=True)

Make a WCS object and convert HEALPix data into WCS projection.

Parameters

sum_bandsbool, optional

Sum over non-spatial axes before reprojecting. If False then the WCS map will have the same dimensionality as the HEALPix one. Default is False.

normalizebool, optional

Preserve integral by splitting HEALPix values between bins. Default is True.

projstr, optional

WCS-projection. Default is “AIT”.

oversamplefloat, optional

Oversampling factor for WCS map. This will be the approximate ratio of the width of a HEALPix pixel to a WCS pixel. If this parameter is None then the width will be set from width_pix. Default is 2.

width_pixint, optional

Width of the WCS geometry in pixels. The pixel size will be set to the number of pixels satisfying oversample or width_pix whichever is smaller. If this parameter is None then the width will be set from oversample. Default is None.

hpx2wcsHpxToWcsMapping, optional

Set the HEALPix to WCS mapping object that will be used to generate the WCS map. If None then a new mapping will be generated based on proj and oversample arguments. Default is None.

Returns

map_outWcsMap

WCS map object.

to_wcs_tiles(nside_tiles=4, margin='0 deg', method='nearest', oversampling_factor=1)

Convert HpxNDMap to a list of WCS tiles.

Parameters

nside_tilesint, optional

HEALPix NSIDE parameter for super pixel tiles. Default is 4.

marginAngle, optional

Width margin of the WCS tile. Default is “0 deg”.

method{‘nearest’, ‘linear’}, optional

Interpolation method. Default is “nearest”.

oversampling_factorint, optional

Oversampling factor. Default is 1.

Returns

wcs_tileslist of WcsNDMap

WCS tiles.

upsample(factor, order=0, preserve_counts=True, axis_name=None)

Upsample the spatial dimension by a given factor.

Parameters

factorint

Upsampling factor.

orderint, optional

Order of the interpolation used for upsampling. Default is 0.

preserve_countsbool, optional

Preserve the integral over each bin. This should be true if the map is an integral quantity (e.g. counts) and false if the map is a differential quantity (e.g. intensity). Default is True.

axis_namestr, optional

Which axis to upsample. By default, spatial axes are upsampled. Default is None.

Returns

mapMap

Upsampled map.

write(filename, overwrite=False, **kwargs)

Write to a FITS file.

Parameters

filenamestr

Output file name.

overwritebool, optional

Overwrite existing file. Default is False.

hdustr, optional

Set the name of the image extension. By default, this will be set to ‘SKYMAP’ (for BINTABLE HDU) or ‘PRIMARY’ (for IMAGE HDU).

hdu_bandsstr, optional

Set the name of the bands table extension. Default is ‘BANDS’.

formatstr, optional

FITS format convention. By default, files will be written to the gamma-astro-data-formats (GADF) format. This option can be used to write files that are compliant with format conventions required by specific software (e.g. the Fermi Science Tools). The following formats are supported:

• “gadf” (default)

• “fgst-ccube”

• “fgst-ltcube”

• “fgst-bexpcube”

• “fgst-srcmap”

• “fgst-template”

• “fgst-srcmap-sparse”

• “galprop”

• “galprop2”

sparsebool, optional

Sparsify the map by dropping pixels with zero amplitude. This option is only compatible with the ‘gadf’ format.

checksumbool, optional

When True adds both DATASUM and CHECKSUM cards to the headers written to the file. Default is False.