Sets attributes of a source dataset.
sherpa> SETDATA [#] <arg> = <numeric>
where # specifies the number of the background dataset (default dataset
number is 1).
The argument <arg> is one of the following options:
SETDATA Command Arguments
| BACKSCALE |
A normalizing quantity which can indicate the the ratio of the
area of the source extraction region in an image to the full image
area. |
| TIME |
The exposure time of the source observation. |
The primary use of this command is to set the attributes of non-PHA
datasets (e.g. ASCII datasets). Setting TIME
affects the normalization of the source model, which is entered with
the SOURCE command.
Setting BACKSCAL affects the relative normalization
of the background model when it is applied to a source region.
For instance, if the background model amplitude in a background dataset bin is
M_B, the BACKSCAL of that dataset is
B_B, and the BACKSCAL of the source dataset
is B_S, then the contribution of the background to the
source region spectrum is
For related information, see SETBACK.
Set the time of an input ASCII dataset:
sherpa> READ DATA example1.dat
sherpa> PARAMPROMPT OFF
sherpa> SOURCE = POLY[p]
sherpa> THAW p.c1 p.c2
sherpa> FIT
LVMQT: V2.0
LVMQT: initial statistic value = 325.453
LVMQT: final statistic value = 0.255412 at iteration 2
p.c0 0.305218
p.c1 -0.142263
p.c2 1.01643
sherpa> SETDATA TIME = 100
sherpa> FIT
LVMQT: V2.0
LVMQT: initial statistic value = 1.43934e+06
LVMQT: final statistic value = 0.255412 at iteration 3
p.c0 0.00292297
p.c1 -0.00133705
p.c2 0.0101542
Set the times and backscales for an input dataset with mean amplitude
60 counts and a background dataset with mean amplitude 20 counts:
sherpa> DATA spec.dat
sherpa> BACK back.dat
sherpa> PARAMPROMPT OFF
sherpa> SOURCE = CONST[co]
sherpa> BG = CONST[bo]
sherpa> FIT
LVMQT: V2.0
LVMQT: initial statistic value = 980.167
LVMQT: final statistic value = 142.424 at iteration 3
co.c0 39.3331
bo.c0 18.4647
sherpa> SETDATA TIME = 10
sherpa> SETDATA BACKSCALE = .1
sherpa> SETBACK TIME = 100
sherpa> SETBACK BACKSCALE = .25
sherpa> bo.c0.min = 0
sherpa> FIT
LVMQT: V2.0
LVMQT: initial statistic value = 7.34745e+07
LVMQT: final statistic value = 142.424 at iteration 3
co.c0 5.70591
bo.c0 0.0738588
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load_rmf,
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set_axes,
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set_exptime,
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set_weights,
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