NAME

ftaddarf -- Add input ARF files with specified weights.

USAGE

ftaddarf infiles weights outfile
or,
ftaddarf @infile outfile=outfile

DESCRIPTION

FTADDARF sums input ARF files with specified weights, and outputs a single ARF. This task may be used when combining several spectral files having different ARFs but an identical RMF. For example, when combining energy spectra taken at different pointing positions with the same detector, and adding spectral files taken simultaneously with plural detectors having different ARFs but the same RMF. Users are WARNED that the use of this task in inappropriate circumstances can (and most likely WILL) lead to extremely misleading results.

PARAMETERS

list [string]
ARF files to be added together. The input to this parameter can either be a list of ARF files, or can be the name of an ASCII file containing such a list of files (one per line) and weighting factors for the ARFs. The weighting factors should be followed by a blank after each ARF file and should be real. In case of, an ascii file is used, the name of the ASCII file should be preceeded by a, '@' (eg @file_list instructs the task to open the ASCII file file_list, and read the ARF filenames from it).

weights [string]
Relative weighting factors for the ARFs given via the list parameter. User is asked for this parameter when name of ARFs are given and not the ascii file. The number of values and ordering MUST be the same as for the filenames specified by the list parameter. The input to this parameter is a list of reals.

outfile [filename]
The name of the ARF file to be created. For safety, the name of the o/p file CANNOT be the same as one of the i/p files, and the task will stop if this is the case. Under unix/ultrix, an o/p filename identical to a file which already exists on disk is also considered illegal, and the task will stop. However, the existing file can be automatically removed, and the new file written if the o/p filename is preceeded by "!" at the outfile prompt.

(clobber = no) [boolean]
Standard HEAdas clobber parameter; controls whether an existing output file may be overwritten.

(history = yes) [boolean]
Standard HEAdas history parameter; controls whether the runtime parameter values should be written in block of HISTORY keywords in the output file.

EXAMPLES

A) Average gis2.arf and gis3.arf and write to gis23.arf, specifying everything on the command line. 

     ftaddarf 'gis2.arf gis3.arf' '0.5 0.5' gis23.arf
or 
     ftaddarf gis2.arf,gis3.arf 0.5,0.5 gis23.arf
B) Add the files listed in text file arfs.ascii, using the weighting factors listed in text file weights.ascii, with the output overwriting an existing file called sum.arf 
     prompt> ftaddarf
     ** ftaddarf 2.0
     List of i.p ARFs to be added[] @arfs.ascii
     Name of output ARF to be created[] !sum.arf

LIMITATIONS

The inappropriate use of this task will most likely give rise to extremely misleading results. Care should be exercised. The summation is not carried out unless number of energy bins and all the ENERG_LO and ENERG_HI values are identical for all the input files. The TELESCOP and INSTRUME values can be different for input files. In this case, values in the first file are written in the output ARF.

LAST MODIFIED

August 2013