MapAxis¶
-
class
gammapy.maps.
MapAxis
(nodes, interp='lin', name='', node_type='edges', unit='')[source]¶ Bases:
object
Class representing an axis of a map.
Provides methods for transforming to/from axis and pixel coordinates. An axis is defined by a sequence of node values that lie at the center of each bin. The pixel coordinate at each node is equal to its index in the node array (0, 1, ..). Bin edges are offset by 0.5 in pixel coordinates from the nodes such that the lower/upper edge of the first bin is (-0.5,0.5).
- Parameters
- nodes
ndarray
orQuantity
Array of node values. These will be interpreted as either bin edges or centers according to
node_type
.- interpstr
Interpolation method used to transform between axis and pixel coordinates. Valid options are ‘log’, ‘lin’, and ‘sqrt’.
- namestr
Axis name
- node_typestr
Flag indicating whether coordinate nodes correspond to pixel edges (node_type = ‘edge’) or pixel centers (node_type = ‘center’). ‘center’ should be used where the map values are defined at a specific coordinate (e.g. differential quantities). ‘edge’ should be used where map values are defined by an integral over coordinate intervals (e.g. a counts histogram).
- unitstr
String specifying the data units.
- nodes
Attributes Summary
Array of bin widths.
Return array of bin centers.
Return array of bin edges.
Interpolation scale of the axis.
Name of the axis.
Return number of bins.
Return node type (‘center’ or ‘edge’).
Return coordinate axis unit.
Methods Summary
coord_to_idx
(self, coord[, clip])Transform from axis coordinate to bin index.
coord_to_pix
(self, coord)Transform from axis to pixel coordinates.
copy
(self, \*\*kwargs)Copy
MapAxis
instance and overwrite given attributes.downsample
(self, factor)Downsample map axis by a given factor.
from_bounds
(lo_bnd, hi_bnd, nbin, \*\*kwargs)Generate an axis object from a lower/upper bound and number of bins.
from_edges
(edges, \*\*kwargs)Generate an axis object from a sequence of bin edges.
from_energy_bounds
(emin, emax, nbin[, unit, …])Make an energy axis.
from_nodes
(nodes, \*\*kwargs)Generate an axis object from a sequence of nodes (bin centers).
group_table
(self, edges)Compute bin groups table for the map axis, given coarser bin edges.
pix_to_coord
(self, pix)Transform from pixel to axis coordinates.
slice
(self, idx)Create a new axis object by extracting a slice from this axis.
squash
(self)Create a new axis object by squashing the axis into one bin.
upsample
(self, factor)Upsample map axis by a given factor.
Attributes Documentation
-
bin_width
¶ Array of bin widths.
-
center
¶ Return array of bin centers.
-
edges
¶ Return array of bin edges.
-
interp
¶ Interpolation scale of the axis.
-
name
¶ Name of the axis.
-
nbin
¶ Return number of bins.
-
node_type
¶ Return node type (‘center’ or ‘edge’).
-
unit
¶ Return coordinate axis unit.
Methods Documentation
-
copy
(self, **kwargs)[source]¶ Copy
MapAxis
instance and overwrite given attributes.- Parameters
- **kwargsdict
Keyword arguments to overwrite in the map axis constructor.
- Returns
- copy
MapAxis
Copied map axis.
- copy
-
downsample
(self, factor)[source]¶ Downsample map axis by a given factor.
- Parameters
- factorint
Downsampling factor.
- Returns
- axis
MapAxis
Downsampled map axis.
- axis
-
classmethod
from_bounds
(lo_bnd, hi_bnd, nbin, **kwargs)[source]¶ Generate an axis object from a lower/upper bound and number of bins.
If node_type = ‘edge’ then bounds correspond to the lower and upper bound of the first and last bin. If node_type = ‘center’ then bounds correspond to the centers of the first and last bin.
- Parameters
- lo_bndfloat
Lower bound of first axis bin.
- hi_bndfloat
Upper bound of last axis bin.
- nbinint
Number of bins.
- interp{‘lin’, ‘log’, ‘sqrt’}
Interpolation method used to transform between axis and pixel coordinates. Default: ‘lin’.
-
classmethod
from_edges
(edges, **kwargs)[source]¶ Generate an axis object from a sequence of bin edges.
This method should be used to construct an axis where the bin edges should lie at specific values (e.g. a histogram). The number of bins will be one less than the number of edges.
- Parameters
- edges
ndarray
Axis bin edges.
- interp{‘lin’, ‘log’, ‘sqrt’}
Interpolation method used to transform between axis and pixel coordinates. Default: ‘lin’.
- edges
-
classmethod
from_energy_bounds
(emin, emax, nbin, unit=None, per_decade=False, name=None)[source]¶ Make an energy axis.
Used frequently also to make energy grids, by making the axis, and then using
axis.center
oraxis.edges
.
-
classmethod
from_nodes
(nodes, **kwargs)[source]¶ Generate an axis object from a sequence of nodes (bin centers).
This will create a sequence of bins with edges half-way between the node values. This method should be used to construct an axis where the bin center should lie at a specific value (e.g. a map of a continuous function).
- Parameters
- nodes
ndarray
Axis nodes (bin center).
- interp{‘lin’, ‘log’, ‘sqrt’}
Interpolation method used to transform between axis and pixel coordinates. Default: ‘lin’.
- nodes
-
group_table
(self, edges)[source]¶ Compute bin groups table for the map axis, given coarser bin edges.
-
slice
(self, idx)[source]¶ Create a new axis object by extracting a slice from this axis.
- Parameters
- idxslice
Slice object selecting a subselection of the axis.
- Returns
- axis
MapAxis
Sliced axis object.
- axis