Purpose : Sums spectral components (output from autospec) 
           Data files in plain xyz format
 Usage   : sumspec [options] file1 fac1 file2 fac2 [file3 fac3 ...]

 Options : 
 -i DIR  : pathes are relative to directory DIR
 -o FILE : write to file FILE. The default is: sumspec.pl
 -fac fac  : Use fac as default factor rather than 1.
 -w      : overwrite enabled.
 -g ncos : GNUplot command lines are written to the output file.
           ncos = 0,1,2 is the exponent of the cosine damping function.
           NB: This sets "using 1:(ncos+2)" 
 -a      : GNUplot is called automatically. (sets "-g 1").
 -G      : Plot gridlines. Requires -g or -a option.
 -x xmin xmax : The energy range is set to [xmin,xmax].
                (ignored if neither -g nor -a is set).
 -y ymin ymax : The ordinate scale is set to [ymin,ymax].
                (ignored if neither -g nor -a is set).
 -s shift: Shift the energy scale by -shift 
                (ignored if neither -g nor -a is set).
 -S shift: Shift the energy scale by -shift 
           Similar to -s, but this time the output file is modified.
 -G      : Plot gridlines.
 -n ndata: Read only the first ndata data-sets.
 -ver    : Version information about the program 
 -h      : Print this help text. 
 -?      : Print this help text. 

Example: sumspec -a -G b2u/spectrum.pl 1.0  b2g/spectrum.pl 1.0

Following the options there follow the names of the files containing
the spectral data. For all components a factor, giving the weight,
has to follow the file-name. If a factor is not provided 
it is set to 1 or, if option -fac is given, to fac.
sumspec was designed to sum data generated by autospec.
However, it can also sum other files with a time column and up to 9 data columns.
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