get_axes

Context: data

Synopsis

Return the alternate grid of a data set

Syntax

get_axes( [id, bkg_id] )

Description

The get_axes() function returns the alternate grid of a 1- or 2-D data set by data id or bkg_id. For PHA spectra, the alternate grid corresponds to (E_MIN, E_MAX), the energy grid of the data set. For images, get_axes() returns the axes lengths in the current coordinate system, where the size of each axis array returned matches the size of the corresponding image dimension.

id - the id of the data set to use; if not given, uses the default dataset id (id=1 by default, see "ahelp get_default_id")
bkg_id - the id of the background to use, e.g. if more than one background is associated with the data

Examples

Example 1

sherpa> get_axes()

When called with no arguments, get_axes() returns the (e_min, e_max) grid of the default data set. In this example, data set 1 is a PHA spectrum.

sherpa> print(get_data())
name           = simple.pi
channel        = Float64[1024]
counts         = Float64[1024]
staterror      = None
syserror       = None
bin_lo         = None
bin_hi         = None
grouping       = None
quality        = None
exposure       = 56494.4943719
backscal       = 9.36267570731e-05
areascal       = 1.0
grouped        = False
subtracted     = False
units          = energy
response_ids   = [1]
background_ids = [1]

sherpa> get_axes()
           
(array([  7.3000e-03,   1.4600e-02,   2.9200e-02, ...,   1.4907e+01,
         1.4921e+01,   1.4936e+01]),
 array([  1.4600e-02,   2.9200e-02,   4.3800e-02, ...,   1.4921e+01,
         1.4936e+01,   1.4950e+01]))

Example 2

sherpa> get_axes(2)

If supplied with a data set ID, get_axes() returns the alternate grid of the specified data set. In this example, data set 2 is an image.

sherpa> print(get_data(2))
name      = image.fits
x0        = Float64[56376]
x1        = Float64[56376]
y         = Float64[56376]
shape     = (216, 261)
staterror = None
syserror  = None
sky       = physical
 crval    = [ 3798.5  4019.5]
 crpix    = [ 0.5  0.5]
 cdelt    = [ 2.  2.]
eqpos     = world
 crval    = [ 278.3866  -10.5893]
 crpix    = [ 4096.5  4096.5]
 cdelt    = [-0.0001  0.0001]
 crota    = 0
 epoch    = 2000
 equinox  = 2000
coord     = logical

sherpa> get_axes(2)
            
(array([   1.,    2.,    3., ...,  259.,  260.,  261.]),
 array([   1.,    2.,    3., ...,  214.,  215.,  216.]))

Bugs

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.