# RegionNDMap¶

class gammapy.maps.RegionNDMap(geom, data=None, dtype='float32', meta=None, unit='')[source]

N-dimensional region map. A RegionNDMap owns a RegionGeom instance as well as a data array containing the values associated to that region in the sky along the non-spatial axis, usually an energy axis. The spatial dimensions of a RegionNDMap are reduced to a single spatial bin with an arbitrary shape, and any extra dimensions are described by an arbitrary number of non-spatial axes.

Parameters
geomRegionGeom

Region geometry object.

datandarray

Data array. If none then an empty array will be allocated.

dtypestr, optional

Data type, default is float32

metadict

Dictionary to store meta data.

unitstr or Unit

The map unit

Attributes Summary

 data Data array (ndarray) geom Map geometry (Geom) is_mask Whether map is mask with bool dtype meta Map meta (dict) quantity Map data times unit (Quantity) tag unit Map unit (Unit)

Methods Summary

 apply_edisp(edisp) Apply energy dispersion to map. coadd(map_in[, weights]) Add the contents of map_in to this map. copy(**kwargs) Copy map instance and overwrite given attributes, except for geometry. create(region[, axes, dtype, meta, unit, …]) Create an empty region map object. Crop the spatial dimensions of the map. cumsum(axis_name) Compute cumulative sum along a given axis cutout(*args, **kwargs) Return self downsample(factor[, preserve_counts, …]) Downsample the non-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) Fill event coordinates (EventList). from_geom(geom[, meta, data, unit, dtype]) Generate an empty map from a Geom instance. from_hdulist(hdulist[, format, ogip_column, hdu]) Create from HDUList. from_images(images[, axis]) Create Map from list of images and a non-spatial axis. get_by_coord(coords[, fill_value]) Return map values at the given map coordinates. get_by_idx(idxs) 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. Return spatial map at the given axis pixel indices. Return spatial map at the given axis pixel coordinates get_spectrum(*args, **kwargs) Return self 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. 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([ax]) Plot the data contained in region map along the non-spatial axis. plot_grid([figsize, ncols]) Plot map as a grid of subplots for non-spatial axes plot_hist([ax]) Plot as histogram. Plot map with interactive widgets to explore the non spatial axes. plot_region([ax]) Plot region read(filename[, format, ogip_column, hdu]) Read from 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 resample_axis(axis[, weights, ufunc]) Resample map to a new axis binning by grouping over smaller bins and apply ufunc to the bin contents. set_by_coord(coords, vals) Set pixels at coords with given vals. set_by_idx(idx, value) 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. stack(other[, weights]) Stack other region map into map. sum_over_axes([axes_names, keepdims, weights]) To sum map values over all non-spatial axes. to_cube(axes) Append non-spatial axes to create a higher-dimensional Map. to_hdulist([format, hdu]) Convert to HDUList. to_region_nd_map(*args, **kwargs) to_table([format]) Convert to Table. upsample(factor[, preserve_counts, axis_name]) Upsample the non-spatial dimension by a given factor. write(filename[, overwrite, format, hdu]) Write map to file

Attributes Documentation

data

Data array (ndarray)

geom

Map geometry (Geom)

is_mask

Whether map is mask with bool dtype

meta

Map meta (dict)

quantity

Map data times unit (Quantity)

tag = 'map'
unit

Map unit (Unit)

Methods Documentation

apply_edisp(edisp)

Apply energy dispersion to map. Requires energy axis.

Parameters
edispgammapy.irf.EDispKernel

Energy dispersion matrix

Returns
mapWcsNDMap

Map with energy dispersion applied.

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

Input map.

weights: Map or ~numpy.ndarray

copy(**kwargs)

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

Parameters
**kwargsdict

Keyword arguments to overwrite in the map constructor.

Returns
copyMap

Copied Map.

classmethod create(region, axes=None, dtype='float32', meta=None, unit='', wcs=None, binsz_wcs='0.1deg', data=None)[source]

Create an empty region map object.

Parameters
regionstr or SkyRegion

Region specification

axeslist of MapAxis

Non spatial axes.

dtypestr

Data type, default is ‘float32’

unitstr or Unit

Data unit.

metadict

Dictionary to store meta data.

wcsWCS

WCS projection to use for local projections of the region

datandarray

Data array

Returns
mapRegionNDMap

Region map

crop()[source]

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 integrate.

Returns
cumsumMap

Map with cumulative sum

cutout(*args, **kwargs)[source]

Return self

downsample(factor, preserve_counts=True, axis_name='energy', weights=None)[source]

Downsample the non-spatial dimension by a given factor.

Parameters
factorint

Downsampling factor.

preserve_countsbool

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).

axis_namestr

Which axis to downsample. Default is “energy”.

weightsRegionNDMap

Contains the weights to apply to the axis to reduce. Default is just weighs of one.

Returns
mapRegionNDMap

Downsampled region 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

Weights vector. Default is weight of one.

fill_by_idx(idx, weights=None)[source]

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

Weights vector. Default is weight of one.

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

Weights vector. Default is weight of one.

fill_events(events)

Fill event coordinates (EventList).

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

Generate an empty map from a Geom instance.

Parameters
geomGeom

Map geometry.

datanumpy.ndarray

data array

metadict

Dictionary to store meta data.

unitstr or Unit

Data unit.

Returns
map_outMap

Map object

classmethod from_hdulist(hdulist, format='gadf', ogip_column=None, hdu=None, **kwargs)[source]

Create from HDUList.

Parameters
hdulistHDUList

HDU list.

Format specification

ogip_column{“COUNTS”, “QUALITY”, “BACKSCAL”}

If format ‘ogip’ is chosen which table hdu column to read.

hdustr

Name or index of the HDU with the map data.

Returns
region_nd_mapRegionNDMap

Region map.

classmethod from_images(images, axis=None)

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

If the images have a non-spatial axis of length 1 a new axes is generated from by merging the individual axes. The image geometries must be aligned.

Parameters
imageslist of Map objects

Images

axisMapAxis

Map axis

Returns
mapMap

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 of the projection footprint

Returns
valsndarray

Values of pixels in the map. np.nan used to flag coords outside of map.

get_by_idx(idxs)[source]

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. np.nan used to flag coordinate outside of 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 of the projection footprint

Returns
valsndarray

Array of pixel values. np.nan used to flag coordinates outside of 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. Dict 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.

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.

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.

get_spectrum(*args, **kwargs)[source]

Return self

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

Coordinates at which to evaluate the IRF

Returns
arrayQuantity

Returns 2D array with axes offset

interp_by_coord(coords, method='linear', fill_value=None)[source]

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{“nearest”, “linear”}

Method to interpolate data values. By default no interpolation is performed and the return value will be the amplitude of the pixel encompassing the given coordinate.

fill_valueNone or float value

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

Returns
valsndarray

Interpolated pixel values.

interp_by_pix(pix, method='linear', fill_value=None)[source]

Interpolate map values at the given pixel coordinates.

Parameters
pixtuple

Tuple of pixel coordinate arrays for each dimension of the map. Tuple should be ordered as (p_lon, p_lat, p_0, …, p_n) where p_i are pixel coordinates for non-spatial dimensions of the map.

method{“nearest”, “linear”}

Method to interpolate data values. By default no interpolation is performed and the return value will be the amplitude of the pixel encompassing the given coordinate.

fill_valueNone or float value

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

Returns
valsndarray

Interpolated pixel values.

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

Interpolate map to input geometry.

Parameters
geomGeom

Target Map geometry

preserve_countsbool

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)

**kwargsdict

Keyword arguments passed to Map.interp_by_coord

Returns
interp_mapMap

Interpolated Map

iter_by_image()

Iterate over image planes of the map.

This is a generator yielding (data, idx) tuples, 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.

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

mask_nearest_position(position)

Given a sky coordinate return nearest valid position in the mask

Parameters
positionSkyCoord

Test position

Returns
positionSkyCoord

normalize(axis_name=None)

Normalise data in place along a given axis.

Parameters
axis_namestr

Along which axis to normalize.

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

Pad the spatial dimensions of the map.

Parameters

Number of pixels padded to the edges of each axis.

axis_namestr

Which axis to downsample. By default spatial axes are padded.

mode{‘edge’, ‘constant’, ‘interp’}

cvalfloat

Returns
mapMap

plot(ax=None, **kwargs)[source]

Plot the data contained in region map along the non-spatial axis.

Parameters
axAxis

Axis used for plotting

**kwargsdict

Keyword arguments passed to errorbar

Returns
axAxis

Axis used for plotting

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

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

Parameters
figsizetuple of int

Figsize to plot on

ncolsint

Number of columns to plot

**kwargsdict

Keyword arguments passed to Map.plot.

Returns
axesndarray of Axes

Axes grid

plot_hist(ax=None, **kwargs)[source]

Plot as histogram.

kwargs are forwarded to hist

Parameters
axaxis (optional)

Axis instance to be used for the plot

**kwargsdict

Keyword arguments passed to hist

Returns
axAxis

Axis used for plotting

plot_interactive()[source]

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

Parameters
rc_paramsdict

Passed to matplotlib.rc_context(rc=rc_params) to style the plot.

**kwargsdict

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



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_region(ax=None, **kwargs)[source]

Plot region

Parameters
axWCSAxes

Axes to plot on. If no axes are given, the region is shown using the minimal equivalent WCS geometry.

**kwargsdict

Keyword arguments forwarded to as_artist

classmethod read(filename, format='gadf', ogip_column=None, hdu=None)[source]

Parameters
filenamepathlib.Path or str

Filename.

Which format to use.

ogip_column{None, “COUNTS”, “QUALITY”, “BACKSCAL”}

If format ‘ogip’ is chosen which table hdu column to read.

hdustr

Name or index of the HDU with the map data.

Returns
region_mapRegionNDMap

Region nd map

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

Function to use for reducing the data.

keepdimsbool, optional

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

weightsMap

Weights to be applied.

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

Function to use for reducing the data.

keepdimsbool, optional

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

axes_names: list

Names of MapAxis to reduce over If None, all will reduced

weightsMap

Weights to be applied.

Returns
map_outMap

Map with non-spatial axes reduced

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

Resample map to a new axis binning by grouping over smaller bins and apply ufunc to the bin contents.

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

Parameters
axisMapAxis

New map axis.

weightsMap

Array to be used as weights. The spatial geometry must be equivalent to other and additional axes must be broadcastable.

ufuncufunc

ufunc to use to resample the axis. Default is numpy.add.

Returns
mapMap

Map with resampled axis.

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, value)[source]

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

Dict 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 dict are kept unchanged.

Returns
map_outMap

Sliced map object.

stack(other, weights=None)[source]

Stack other region map into map.

Parameters
otherRegionNDMap

Other map to stack

weightsRegionNDMap

Array to be used as weights. The spatial geometry must be equivalent to other and additional axes must be broadcastable.

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

To sum map values over all non-spatial axes.

Parameters
keepdimsbool, optional

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

axes_names: list of str

Names of MapAxis to reduce over. If None, all will summed over

weightsMap

Weights to be applied. The Map should have the same geometry.

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 the new geometry

Parameters
axeslist

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

Returns
mapWcsNDMap

new map

to_hdulist(format='gadf', hdu='SKYMAP')[source]

Convert to HDUList.

Parameters

Format specification

hdustr

Name of the HDU with the map data, used for “gadf” format.

Returns
hdulistHDUList

HDU list

to_region_nd_map(*args, **kwargs)[source]
to_table(format='gadf')[source]

Convert to Table.

Data format specification: PHA

Parameters

Format specification

Returns
tableTable

Table

upsample(factor, preserve_counts=True, axis_name='energy')[source]

Upsample the non-spatial dimension by a given factor.

Parameters
factorint

Upsampling factor.

preserve_countsbool

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

axis_namestr

Which axis to upsample. Default is “energy”.

Returns
mapRegionNDMap

Upsampled region map.

write(filename, overwrite=False, format='gadf', hdu='SKYMAP')[source]

Write map to file

Parameters
filenamepathlib.Path or str

Filename.