Specifies the coordinate system for use in fits to 2-D images.
sherpa> COORD [<dataset range> | ALLSETS] [<arg>]
where <dataset range> = #, or more generally #:#,#:#,..., such that #
specifies a dataset number, and #:# represents an inclusive range of
datasets; one may specify multiple inclusive ranges by separating them
with commas. The default dataset is dataset number 1.
<arg> is either:
COORD Command Arguments
| {IMAGE | LOGICAL} |
Logical coordinates: the bin numbers (1, 2, 3...) |
| PHYSICAL |
Physical coordinates: a linear transformation of logical coordinates. |
| {WCS | WORLD} |
World coordinates (RA,dec). |
Issuing the COORD command
with no argument causes Sherpa to display the
current setting for the specified dataset number(s).
Note that if, e.g., a source model is defined
before a switch of coordinate systems,
it will be necessary either to issue the GUESS command to reset the
initial parameter values and their ranges to more appropriate values,
or to reset the values by hand.
Fit data in physical coordinates:
sherpa> DATA example_img2.fits
sherpa> NOTICE FILTER "circle(425,343,30)"
sherpa> PARAMPROMPT OFF
sherpa> SOURCE = GAUSS2D[g]
sherpa> COORD
Coordinate setting for dataset 1: logical
sherpa> COORD PHYSICAL
sherpa> GUESS SOURCE
sherpa> COORD
Coordinate setting for dataset 1: physical
sherpa> g.fwhm = 1
sherpa> FIT
LVMQT: V2.0
LVMQT: initial statistic value = 1289.82
LVMQT: final statistic value = 1176.13 at iteration 12
g.fwhm 2.39494
g.xpos 4010.48
g.ypos 3927.48
g.ampl 40.3545
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