RegionGeom#

class gammapy.maps.RegionGeom(region, axes=None, wcs=None, binsz_wcs='0.1 deg')[source]#

Bases: Geom

Map geometry representing a region on the sky.

The spatial component of the geometry is made up of a single pixel with an arbitrary shape and size. It can also have any number of non-spatial dimensions. This class represents the geometry for the RegionNDMap maps.

Parameters:

regionSkyRegion: Region object.
axeslist of MapAxis: Non-spatial data axes.
wcsWCS: Optional WCS object to project the region if needed.
binsz_wcsQuantity: Angular bin size of the underlying WcsGeom used to evaluate quantities in the region. Default is “0.1 deg”. This default value is adequate for the majority of use cases. If a WCS object is provided, the input of binsz_wcs is overridden.

Attributes Summary

`as_energy_true`	If the geom contains an axis named 'energy' rename it to 'energy_true'.
`axes`	List of non-spatial axes.
`axes_names`	All axes names.
`binsz_wcs`	Angular bin size of the underlying `WcsGeom`.
`center_coord`	Center coordinate of the region as a `astropy.coordinates.SkyCoord`.
`center_pix`	Pixel values corresponding to the center of the region.
`center_skydir`	Sky coordinate of the center of the region.
`data_shape`	Shape of the `ndarray` matching this geometry.
`data_shape_axes`	Shape of data of the non-spatial axes and unit spatial axes.
`frame`	Coordinate system, either Galactic ("galactic") or Equatorial ("icrs").
`has_energy_axis`	Whether geom has an energy axis (either 'energy' or 'energy_true').
`is_all_point_sky_regions`	Whether regions are all point regions.
`is_allsky`
`is_flat`	Whether the geom non-spatial axes have length 1, equivalent to an image.
`is_hpx`
`is_image`	Whether the geom is an image without extra dimensions.
`is_region`
`is_regular`
`npix`	Number of spatial pixels.
`projection`
`region`	The spatial component of the region geometry as a `SkyRegion`.
`wcs`	WCS projection object.
`width`	Width of bounding box of the region.

Methods Summary

`bin_volume`()	If the `RegionGeom` has a non-spatial axis, it returns the volume of the region.
`contains`(coords)	Check if a given map coordinate is contained in the region.
`contains_pix`(pix)	Check if a given pixel coordinate is contained in the geometry.
`contains_wcs_pix`(pix)	Check if a given WCS pixel coordinate is contained in the region.
`coord_to_idx`(coords[, clip])	Convert map coordinates to pixel indices.
`coord_to_pix`(coords)	Convert map coordinates to pixel coordinates.
`copy`(**kwargs)	Copy and overwrite given attributes.
`create`(region, **kwargs)	Create region geometry.
`crop`()	Crop the geometry at the edges.
`data_nbytes`([dtype])	Estimate memory usage in megabytes of the Numpy data array matching this geometry depending on the given type.
`downsample`(factor, axis_name)	Downsample a non-spatial dimension of the region by a given factor.
`drop`(axis_name)	Drop an axis from the geom.
`energy_mask`([energy_min, energy_max, ...])	Create a mask for a given energy range.
`from_hdulist`(hdulist[, format, hdu])	Read region table and convert it to region list.
`from_regions`(regions, **kwargs)	Create region geometry from list of regions.
`get_coord`([mode, frame, sparse, axis_name])	Get map coordinates from the geometry.
`get_idx`()	Get tuple of pixel indices for this geometry.
`get_wcs_coord_and_weights`([factor])	Get the array of spatial coordinates and corresponding weights.
`is_allclose`(other[, rtol_axes, atol_axes])	Compare two data IRFs for equivalency.
`pad`(pad_width, axis_name)	Pad the geometry at the edges.
`pix_to_coord`(pix)	Convert pixel coordinates to map coordinates.
`pix_to_idx`(pix[, clip])	Convert pixel coordinates to pixel indices.
`plot_region`([ax, kwargs_point, path_effect])	Plot region in the sky.
`rename_axes`(names, new_names)	Rename axes contained in the geometry.
`replace_axis`(axis)	Replace axis with a new one.
`resample_axis`(axis)	Resample geom to a new axis binning.
`separation`(position)	Angular distance between the center of the region and the given position.
`slice_by_idx`(slices)	Create a new geometry by slicing the non-spatial axes.
`solid_angle`()	Get solid angle of the region.
`squash`(axis_name)	Squash geom axis.
`to_bands_hdu`([hdu_bands, format])
`to_binsz`(binsz)	Return self.
`to_binsz_wcs`(binsz)	Change the bin size of the underlying WCS geometry.
`to_cube`(axes)	Append non-spatial axes to create a higher-dimensional geometry.
`to_hdulist`([format, hdu_bands, hdu_region])	Convert geometry to HDU list.
`to_image`()	Remove non-spatial axes to create a 2D region.
`to_wcs_geom`([width_min])	Get the minimal equivalent geometry which contains the region.
`union`(other)	Stack a `RegionGeom` by making the union.
`upsample`(factor[, axis_name])	Upsample a non-spatial dimension of the region by a given factor.

Attributes Documentation

as_energy_true#: If the geom contains an axis named ‘energy’ rename it to ‘energy_true’.

axes#: List of non-spatial axes.

axes_names#: All axes names.

binsz_wcs#

Angular bin size of the underlying WcsGeom.

Returns:

binsz_wcs: Angle: Angular bin size.

center_coord#: Center coordinate of the region as a astropy.coordinates.SkyCoord.

center_pix#: Pixel values corresponding to the center of the region.

center_skydir#: Sky coordinate of the center of the region.

data_shape#: Shape of the ndarray matching this geometry.

data_shape_axes#: Shape of data of the non-spatial axes and unit spatial axes.

frame#: Coordinate system, either Galactic (“galactic”) or Equatorial (“icrs”).

has_energy_axis#: Whether geom has an energy axis (either ‘energy’ or ‘energy_true’).

is_all_point_sky_regions#: Whether regions are all point regions.

is_allsky = False#

is_flat#: Whether the geom non-spatial axes have length 1, equivalent to an image.

is_hpx = False#

is_image#: Whether the geom is an image without extra dimensions.

is_region = True#

is_regular = True#

npix#: Number of spatial pixels.

projection = 'TAN'#

region#: The spatial component of the region geometry as a SkyRegion.

wcs#: WCS projection object.

width#

Width of bounding box of the region.

Returns:

widthQuantity: Dimensions of the region in both spatial dimensions. Units: deg

Methods Documentation

bin_volume()[source]#

If the RegionGeom has a non-spatial axis, it returns the volume of the region. If not, it returns the solid angle size.

Returns:

volumeQuantity: Volume of the region.

contains(coords)[source]#

Check if a given map coordinate is contained in the region.

Requires the region attribute to be set. For PointSkyRegion the method always returns True.

Parameters:

coordstuple, dict, MapCoord or SkyCoord: Object containing coordinate arrays we wish to check for inclusion in the region.

Returns:

maskndarray: Boolean array with the same shape as the input that indicates which coordinates are inside the region.

contains_pix(pix)#

Check if a given pixel coordinate is contained in the geometry.

Parameters:

pixtuple: Tuple of pixel coordinates.

Returns:

containmentndarray: Bool array.

contains_wcs_pix(pix)[source]#

Check if a given WCS pixel coordinate is contained in the region.

For PointSkyRegion the method always returns True.

Parameters:

pixtuple: Tuple of pixel coordinates.

Returns:

containmentndarray: Boolean array.

coord_to_idx(coords, clip=False)#

Convert map coordinates to pixel indices.

Parameters:

coordstuple or MapCoord: Coordinate values in each dimension of the map. This can either be a tuple of numpy arrays or a MapCoord object. If passed as a tuple then the ordering should be (longitude, latitude, c_0, …, c_N) where c_i is the coordinate vector for axis i.
clipbool: Choose whether to clip indices to the valid range of the geometry. If False then indices for coordinates outside the geometry range will be set -1. Default is False.

Returns:

pixtuple: Tuple of pixel indices in image and band dimensions. Elements set to -1 correspond to coordinates outside the map.

coord_to_pix(coords)[source]#

Convert map coordinates to pixel coordinates.

Parameters:

coordstuple: Coordinate values in each dimension of the map. This can either be a tuple of numpy arrays or a MapCoord object. If passed as a tuple then the ordering should be (longitude, latitude, c_0, …, c_N) where c_i is the coordinate vector for axis i.

Returns:

pixtuple: Tuple of pixel coordinates in image and band dimensions.

copy(**kwargs)#

Copy and overwrite given attributes.

Parameters:

**kwargsdict: Keyword arguments to overwrite in the map geometry constructor.

Returns:

copyGeom: Copied map geometry.

classmethod create(region, **kwargs)[source]#

Create region geometry.

The input region can be passed in the form of a ds9 string and will be parsed internally by parse. See:

Parameters:

regionstr or SkyRegion: Region definition.
**kwargsdict: Keyword arguments passed to RegionGeom.__init__.

Returns:

geomRegionGeom: Region geometry.

crop()[source]#

Crop the geometry at the edges.

Parameters:

crop_width{sequence, array_like, int}: Number of values cropped from the edges of each axis.

Returns:

geomGeom: Cropped geometry.

data_nbytes(dtype='float32')#

Estimate memory usage in megabytes of the Numpy data array matching this geometry depending on the given type.

Parameters:

dtypestr, optional: The desired data-type for the array. Default is “float32”.

Returns:

memoryQuantity: Estimated memory usage in megabytes (MB).

downsample(factor, axis_name)[source]#

Downsample a non-spatial dimension of the region by a given factor.

Returns:

regionRegionGeom: Region geometry with the downsampled axis.

drop(axis_name)#

Drop an axis from the geom.

Parameters:

axis_namestr: Name of the axis to remove.

Returns:

geomGeom: New geom with the axis removed.

energy_mask(energy_min=None, energy_max=None, round_to_edge=False)#

Create a mask for a given energy range.

The energy bin must be fully contained to be included in the mask.

Parameters:

energy_min, energy_maxQuantity: Energy range.

Returns:

maskMap: Map containing the energy mask. The geometry of the map is the same as the geometry of the instance which called this method.

classmethod from_hdulist(hdulist, format='ogip', hdu=None)[source]#

Read region table and convert it to region list.

Parameters:

hdulistHDUList: HDU list.
format{“ogip”, “ogip-arf”, “gadf”}: HDU format. Default is “ogip”.
hdustr, optional: Name of the HDU. Default is None.

Returns:

geomRegionGeom: Region map geometry.

classmethod from_regions(regions, **kwargs)[source]#

Create region geometry from list of regions.

The regions are combined with union to a compound region.

Parameters:

regionslist of SkyRegion or str: Regions.
**kwargs: dict: Keyword arguments forwarded to RegionGeom.

Returns:

geomRegionGeom: Region map geometry.

get_coord(mode='center', frame=None, sparse=False, axis_name=None)[source]#

Get map coordinates from the geometry.

Parameters:

mode{‘center’, ‘edges’}, optional: Get center or edge coordinates for the non-spatial axes. Default is “center”.
framestr or Frame, optional: Coordinate frame. Default is None.
sparsebool, optional: Compute sparse coordinates. Default is False.
axis_namestr, optional: If mode = “edges”, the edges will be returned for this axis only. Default is None.

Returns:

coordMapCoord: Map coordinate object.

get_idx()[source]#

Get tuple of pixel indices for this geometry.

Returns all pixels in the geometry by default. Pixel indices for a single image plane can be accessed by setting idx to the index tuple of a plane.

Parameters:

idxtuple, optional: A tuple of indices with one index for each non-spatial dimension. If defined only pixels for the image plane with this index will be returned. If none then all pixels will be returned. Default is None.
localbool, optional: Flag to return local or global pixel indices. Local indices run from 0 to the number of pixels in a given image plane. Default is False.
flatbool, optional: Return a flattened array containing only indices for pixels contained in the geometry. Default is False.

Returns:

idxtuple: Tuple of pixel index vectors with one vector for each dimension.

get_wcs_coord_and_weights(factor=10)[source]#

Get the array of spatial coordinates and corresponding weights.

The coordinates are the center of a pixel that intersects the region and the weights that represent which fraction of the pixel is contained in the region.

Parameters:

factorint, optional: Oversampling factor to compute the weights. Default is 10.

Returns:

region_coordMapCoord: MapCoord object with the coordinates inside the region.
weightsndarray: Weights representing the fraction of each pixel contained in the region.

is_allclose(other, rtol_axes=1e-06, atol_axes=1e-06)[source]#

Compare two data IRFs for equivalency.

Parameters:

otherRegionGeom: Region geometry to compare against.
rtol_axesfloat, optional: Relative tolerance for the axes comparison. Default is 1e-6.
atol_axesfloat, optional: Relative tolerance for the axes comparison. Default is 1e-6.

Returns:

is_allclosebool: Whether the geometry is all close.

pad(pad_width, axis_name)#

Pad the geometry at the edges.

Parameters:

pad_width{sequence, array_like, int}: Number of values padded to the edges of each axis.
axis_namestr: Name of the axis to pad.

Returns:

geomGeom: Padded geometry.

pix_to_coord(pix)[source]#

Convert pixel coordinates to map coordinates.

Parameters:

pixtuple: Tuple of pixel coordinates.

Returns:

coordstuple: Tuple of map coordinates.

pix_to_idx(pix, clip=False)[source]#

Convert pixel coordinates to pixel indices.

Returns -1 for pixel coordinates that lie outside the map.

Parameters:

pixtuple: Tuple of pixel coordinates.
clipbool: Choose whether to clip indices to the valid range of the geometry. If False then indices for coordinates outside the geometry range will be set -1. Default is False.

Returns:

idxtuple: Tuple of pixel indices.

plot_region(ax=None, kwargs_point=None, path_effect=None, **kwargs)[source]#

Plot region in the sky.

Parameters:

axWCSAxes, optional: Axes to plot on. If no axes are given, the region is shown using the minimal equivalent WCS geometry. Default is None.
kwargs_pointdict, optional: Keyword arguments passed to Line2D for plotting of point sources. Default is None.
path_effectPathEffect, optional: Path effect applied to artists and lines. Default is None.
**kwargsdict: Keyword arguments forwarded to as_artist.

Returns:

axWCSAxes: Axes to plot on.

rename_axes(names, new_names)#

Rename axes contained in the geometry.

Parameters:

nameslist or str: Names of the axes.
new_nameslist or str: New names of the axes. The list must be of same length than names.

Returns:

geomGeom: Renamed geometry.

replace_axis(axis)#

Replace axis with a new one.

Parameters:

axisMapAxis: New map axis.

Returns:

mapGeom: Geom with replaced axis.

resample_axis(axis)#

Resample geom to a new axis binning.

This method groups the existing bins into a new binning.

Parameters:

axisMapAxis: New map axis.

Returns:

mapGeom: Geom with resampled axis.

separation(position)[source]#

Angular distance between the center of the region and the given position.

Parameters:

positionastropy.coordinates.SkyCoord: Sky coordinate we want the angular distance to.

Returns:

sepAngle: The on-sky separation between the given coordinate and the region center.

slice_by_idx(slices)#

Create a new geometry by slicing the non-spatial axes.

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 dict are kept unchanged.

Returns:

geomGeom: Sliced geometry.

Examples

>>> from gammapy.maps import MapAxis, WcsGeom
>>> import astropy.units as u
>>> energy_axis = MapAxis.from_energy_bounds(1*u.TeV, 3*u.TeV, 6)
>>> geom = WcsGeom.create(skydir=(83.63, 22.01), axes=[energy_axis], width=5, binsz=0.02)
>>> slices = {"energy": slice(0, 2)}
>>> sliced_geom = geom.slice_by_idx(slices)

solid_angle()[source]#

Get solid angle of the region.

Returns:

angleQuantity: Solid angle of the region in steradians. Units: sr

squash(axis_name)#

Squash geom axis.

Parameters:

axis_namestr: Axis to squash.

Returns:

geomGeom: Geom with squashed axis.

to_bands_hdu(hdu_bands=None, format='gadf')#

to_binsz(binsz)[source]#: Return self.

to_binsz_wcs(binsz)[source]#

Change the bin size of the underlying WCS geometry.

Parameters:

binszfloat, str or Quantity: Bin size.

Returns:

regionRegionGeom: Region geometry with the same axes and region as the input, but different WCS pixelization.

to_cube(axes)[source]#

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

Returns:

regionRegionGeom: Region geometry with the added axes.

to_hdulist(format='ogip', hdu_bands=None, hdu_region=None)[source]#

Convert geometry to HDU list.

Parameters:

format{“ogip”, “gadf”, “ogip-sherpa”}: HDU format. Default is “ogip”.
hdu_bandsstr, optional: Name or index of the HDU with the BANDS table. Default is None.
hdu_regionstr, optional: Name or index of the HDU with the region table. Not used for the “gadf” format. Default is None.

Returns:

hdulistHDUList: HDU list.

to_image()[source]#

Remove non-spatial axes to create a 2D region.

Returns:

regionRegionGeom: Region geometry without any non-spatial axes.

to_wcs_geom(width_min=None)[source]#

Get the minimal equivalent geometry which contains the region.

Parameters:

width_minQuantity, optional: Minimum width for the resulting geometry. Can be a single number or two, for different minimum widths in each spatial dimension. Default is None.

Returns:

wcs_geomWcsGeom: A WCS geometry object.

union(other)[source]#: Stack a RegionGeom by making the union.

upsample(factor, axis_name=None)[source]#

Upsample a non-spatial dimension of the region by a given factor.

Returns:

regionRegionGeom: Region geometry with the upsampled axis.

RegionGeom#

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