Geom¶

class gammapy.maps.Geom[source]

Bases: abc.ABC

Map geometry base class.

See also: WcsGeom and HpxGeom

Attributes Summary

 as_energy_true If the geom contains an energy axis rename it to energy true center_coord center_pix center_skydir data_shape Shape of the Numpy data array matching this geometry. has_energy_axis Whether geom has an energy axis is_allsky is_flat Whether the geom non spatial axes have length 1, i.e. is_image Whether the geom is an image without extra dimensions.

Methods Summary

 contains(coords) Check if a given map coordinate is contained in the geometry. Check if a given pixel coordinate is contained in the geometry. 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. crop(crop_width) 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 the spatial dimension of the geometry 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[, hdu, hdu_bands]) Load a geometry object from a FITS HDUList. get_coord([idx, flat]) Get the coordinate array for this geometry. get_idx([idx, local, flat]) Get tuple of pixel indices for this geometry. pad(pad_width, axis_name) Pad the geometry at the edges. Convert pixel coordinates to map coordinates. pix_to_idx(pix[, clip]) Convert pixel coordinates to pixel indices. resample_axis(axis) Resample geom to a new axis binning. slice_by_idx(slices) Create a new geometry by slicing the non-spatial axes. Solid angle (Quantity in sr). squash(axis_name) Squash geom axis. to_bands_hdu([hdu, hdu_skymap, format]) to_cube(axes) Append non-spatial axes to create a higher-dimensional geometry. Create 2D image geometry (drop non-spatial dimensions). upsample(factor, axis_name) Upsample the spatial dimension of the geometry by a given factor.

Attributes Documentation

as_energy_true

If the geom contains an energy axis rename it to energy true

center_coord
center_pix
center_skydir
data_shape

Shape of the Numpy data array matching this geometry.

has_energy_axis

Whether geom has an energy axis

is_allsky
is_flat

Whether the geom non spatial axes have length 1, i.e. if the geom is equivalent to an image.

is_image

Whether the geom is an image without extra dimensions.

Methods Documentation

abstract contains(coords)[source]

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

Parameters
coordstuple or MapCoord

Tuple of map coordinates.

Returns
containmentndarray

Bool array.

contains_pix(pix)[source]

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

Parameters
pixtuple

Tuple of pixel coordinates.

Returns
containmentndarray

Bool array.

coord_to_idx(coords, clip=False)[source]

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.

Returns
pixtuple

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

abstract 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)[source]

Copy and overwrite given attributes.

Parameters
**kwargsdict

Keyword arguments to overwrite in the map geometry constructor.

Returns
copyGeom

Copied map geometry.

abstract crop(crop_width)[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')[source]

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

Parameters
dtypedata-type

The desired data-type for the array. Default is “float32”

Returns
memoryQuantity

Estimated memory usage in megabytes (MB)

abstract downsample(factor, axis_name)[source]

Downsample the spatial dimension of the geometry by a given factor.

Parameters
factorint

Downsampling factor.

axis_namestr

Axis to downsample.

Returns
geomGeom

Downsampled geometry.

drop(axis_name)[source]

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)[source]

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
maskndarray

classmethod from_hdulist(hdulist, hdu=None, hdu_bands=None)[source]

Load a geometry object from a FITS HDUList.

Parameters
hdulistHDUList

HDU list containing HDUs for map data and bands.

hdustr

Name or index of the HDU with the map data.

hdu_bandsstr

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.

Returns
geomGeom

Geometry object.

abstract get_coord(idx=None, flat=False)[source]

Get the coordinate array for this geometry.

Returns a coordinate array with the same shape as the data array. Pixels outside the geometry are set to NaN. Coordinates 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 coordinates for the image plane with this index will be returned. If none then coordinates for all pixels will be returned.

flatbool, optional

Return a flattened array containing only coordinates for pixels contained in the geometry.

Returns
coordstuple

Tuple of coordinate vectors with one vector for each dimension.

abstract get_idx(idx=None, local=False, flat=False)[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.

localbool

Flag to return local or global pixel indices. Local indices run from 0 to the number of pixels in a given image plane.

flatbool, optional

Return a flattened array containing only indices for pixels contained in the geometry.

Returns
idxtuple

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

pad(pad_width, axis_name)[source]

Pad the geometry at the edges.

Parameters

Number of values padded to the edges of each axis.

axis_namestr

Name of the axis to pad.

Returns
geomGeom

abstract pix_to_coord(pix)[source]

Convert pixel coordinates to map coordinates.

Parameters
pixtuple

Tuple of pixel coordinates.

Returns
coordstuple

Tuple of map coordinates.

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

Convert pixel coordinates to pixel indices.

Returns -1 for pixel coordinates that lie outside of 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.

Returns
idxtuple

Tuple of pixel indices.

resample_axis(axis)[source]

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.

slice_by_idx(slices)[source]

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

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
geomGeom

Sliced geometry.

abstract solid_angle()[source]

Solid angle (Quantity in sr).

squash(axis_name)[source]

Squash geom axis.

Parameters
axis_namestr

Axis to squash.

Returns
geomGeom

Geom with squashed axis.

to_bands_hdu(hdu=None, hdu_skymap=None, format='gadf')[source]
abstract to_cube(axes)[source]

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

This will result in 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.

Parameters
axeslist

Axes that will be appended to this geometry.

Returns
geomGeom

Map geometry.

abstract to_image()[source]

Create 2D image geometry (drop non-spatial dimensions).

Returns
geomGeom

Image geometry.

abstract upsample(factor, axis_name)[source]

Upsample the spatial dimension of the geometry by a given factor.

Parameters
factorint

Upsampling factor.

axis_namestr

Axis to upsample.

Returns
geomGeom

Upsampled geometry.