WcsMap#

class gammapy.maps.WcsMap(geom, data, meta=None, unit='')[source]#

Bases: Map

Base class for WCS map classes.

Parameters:

geomWcsGeom: A WCS geometry object.
datandarray: Data array.

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.
`copy`(**kwargs)	Copy map instance and overwrite given attributes, except for geometry.
`create`([map_type, npix, binsz, width, proj, ...])	Factory method to create an empty WCS map.
`crop`(crop_width)	Crop the spatial dimensions of the map.
`cumsum`(axis_name)	Compute cumulative sum along a given axis.
`dot`(other)	Apply dot product with the input map.
`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_hdulist`(hdu_list[, hdu, hdu_bands, format])	Make a WcsMap object from a FITS HDUList.
`from_stack`(maps[, axis, axis_name])	Create Map from a 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`(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.
`iter_by_image_index`()	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_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.
`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.
`reorder_axes`(axes_names)	Return a new map re-ordering the non-spatial axes.
`reproject_by_image`(geom[, preserve_counts, ...])	Reproject each image of a ND map to input 2d geometry.
`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.
`split_by_axis`(axis_name)	Split a Map along an axis into multiple maps.
`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])	Make a FITS HDU from this map.
`to_hdulist`([hdu, hdu_bands, sparse, format])	Convert to `HDUList`.
`to_unit`(unit)	Convert map to a different unit.
`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.

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(map_type='wcs', npix=None, binsz=0.1, width=None, proj='CAR', frame='icrs', refpix=None, axes=None, skydir=None, dtype='float32', meta=None, unit='')[source]#

Factory method to create an empty WCS map.

Parameters:

map_type{‘wcs’, ‘wcs-sparse’}, optional: Map type. Selects the class that will be used to instantiate the map. Default is “wcs”.
npixint or tuple or list, optional: Width of the map in pixels. A tuple will be interpreted as parameters for longitude and latitude axes. For maps with non-spatial dimensions, list input can be used to define a different map width in each image plane. This option supersedes width. Default is None.
binszfloat or tuple or list, optional: Map pixel size in degrees. A tuple will be interpreted as parameters for longitude and latitude axes. For maps with non-spatial dimensions, list input can be used to define a different bin size in each image plane. Default is 0.1.
widthfloat or tuple or list, optional: Width of the map in degrees. A tuple will be interpreted as parameters for longitude and latitude axes. For maps with non-spatial dimensions, list input can be used to define a different map width in each image plane. Default is None.
projstring, optional: Any valid WCS projection type. Default is ‘CAR’ (cartesian).
frame{“icrs”, “galactic”}, optional: Coordinate system, either Galactic (“galactic”) or Equatorial (“icrs”). Default is “icrs”.
refpixtuple, optional: Reference pixel of the projection. If None then this will be chosen to be center of the map. Default is None.
axeslist, optional: List of non-spatial axes. 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 degrees in the coordinate system of the map.
dtypestr, optional: Data type. Default is “float32”.
metadict, optional: Dictionary to store metadata. Default is None.
unitstr or Unit, optional: The unit of the map. Default is “”.

Returns:

mapWcsMap: A WCS map object.

abstract 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.

dot(other)#

Apply dot product with the input map.

The input Map has to share a single MapAxis with the current Map. Because it has no spatial dimension, it must be a RegionNDMap.

Parameters:

otherRegionNDMap: Map to apply the dot product to. It must share a unique non-spatial MapAxis with the current Map.

Returns:

mapMap: Map with dot product applied.

abstract 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.

abstract 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_hdulist(hdu_list, hdu=None, hdu_bands=None, format='gadf')[source]#

Make a WcsMap 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. Default is None.
hdu_bandsstr, optional: Name or index of the HDU with the BANDS table. Default is None.
format{‘gadf’, ‘fgst-ccube’, ‘fgst-template’}, optional: FITS format convention. Default is “gadf”.

Returns:

wcs_mapWcsMap: 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.

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.

abstract 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.

abstract 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.

abstract interp_by_pix(pix, method='linear', fill_value=None)#

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{“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_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. If None, values outside the domain are extrapolated. 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.

iter_by_image_index()#

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:

idxtuple: 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_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)

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

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.
checksumbool: If True checks both DATASUM and CHECKSUM cards in the file headers. Default is False.

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.

reorder_axes(axes_names)#

Return a new map re-ordering the non-spatial axes.

Parameters:

axes_nameslist of str: The list of axes names in the required order.

Returns:

mapMap: The map with axes re-ordered.

reproject_by_image(geom, preserve_counts=False, precision_factor=10)#

Reproject each image of a ND map to input 2d geometry.

For large maps this method is faster than reproject_to_geom.

Parameters:

geomGeom: Target slice geometry in 2D.
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.

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.

abstract 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.

Examples

>>> from gammapy.maps import Map
>>> m = Map.read("$GAMMAPY_DATA/fermi_3fhl/gll_iem_v06_cutout.fits")
>>> slices = {"energy": slice(0, 5)}
>>> sliced = m.slice_by_idx(slices)

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.

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='SKYMAP', hdu_bands=None, sparse=False)[source]#

Make a FITS HDU from this map.

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.

Returns:

hduBinTableHDU or ImageHDU: HDU containing the map data.

to_hdulist(hdu=None, hdu_bands=None, sparse=False, format='gadf')[source]#

Convert to HDUList.

Parameters:

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. Default is None.
sparsebool, optional: Sparsify the map by only writing pixels with non-zero amplitude. Default is False.
format{‘gadf’, ‘fgst-ccube’,’fgst-template’}, optional: FITS format convention. Default is “gadf”.

Returns:

hdu_listHDUList: HDU list.

to_unit(unit)#

Convert map to a different unit.

Parameters:

unitstr or Unit: New unit.

Returns:

mapMap: Map with new unit and converted data.

abstract 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.