Defines an expression to be used to specify the
statistical errors for background data.
The commands BACKERRORS and
BSTATERRORS are equivalent.
sherpa> BERRORS [<dataset range> | ALLSETS] [ID] = <errorExpr>
<dataset range> = # (or more generally #:#,#:#, etc.) 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 1. The ID modifier is used
if and only if the Sherpa state object variable multiback is set to 1,
i.e., if more than one background dataset is to be associated with a
single source dataset. The ID modifier may be any unreserved string
(e.g., A, foo, etc.), i.e., a string that is not a parsable command.
The error expression, <errorExpr>, may be composed of one or
more (algebraically-combined) of the following elements:
| BACK | An input background dataset |
| numericals | Numerical values |
| operators | + - * / ( ) |
A few things to note:
-
Background error expressions cannot be defined without first reading in
a background dataset.
-
The background errors can be
specified in an input file; see READ
BERRORS for more information.
-
If the background errors are not defined using BERRORS or input
using READ BERRORS, then they are computed
as defined for the current statistic; see the documentation on the
STATISTIC command.
See the related command BSYSERRORS.
The background errors are accessible to the Sherpa/S-Lang module
user via the functions
get_berrors and
set_berrors.
Define an expression to be used for the background errors. They are
set to 1.5 in each bin.
sherpa> DATA data.dat
sherpa> BACK back.dat
sherpa> BERRORS = 1.5
Define an expression to be used for the background errors. They are
set to 0.5 times the background datum in each bin.
sherpa> BERRORS = 0.5*BACK
- chandra
-
guide
- sherpa
-
autoest,
back,
bsyserrors,
compute_errors,
compute_statistic,
coord,
covariance,
data,
dataspace,
errors,
fakeit,
feffile,
ftest,
get_paramest,
get_paramestint,
get_paramestlim,
get_paramestreg,
goodness,
group,
guess,
interval-projection,
interval-uncertainty,
is_subtracted,
list_paramest,
load,
load_arf,
load_ascii,
load_back_from,
load_backset,
load_dataset,
load_fitsbin,
load_image,
load_inst,
load_inst_from,
load_pha,
load_pha2,
load_rmf,
mlr,
projection,
read,
region-projection,
region-uncertainty,
restore_paramest,
run_paramest,
run_paramestint,
run_paramestlim,
run_paramestreg,
set_analysis,
set_axes,
set_backscale,
set_coord,
set_data,
set_errors,
set_exptime,
set_subtract,
set_syserrors,
set_weights,
setback,
setdata,
staterrors,
subtract,
syserrors,
uncertainty,
ungroup,
unsubtract,
use
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