#!/usr/bin/env tcsh

set Narg = $#

set fname = "-help"
if ( $Narg > 0 ) then
  set fname = $argv[1]
endif

if ( $Narg == 0 || $fname == "-help" ) then
  echo 'Usage: @1dDiffMag file.1D'
  echo '* Computes a magnitude estimate of the first differences of a 1D file.'
  echo '* Differences are computed down each column.'
  echo '* The result -- a single number -- is on stdout.'
  echo '* But (I hear you say), what IS the result?'
  echo '* For each column, the standard deviation of the first differences is computed.'
  echo '* The final result is the square-root of the sum of the squares of these stdev values.'
  exit 0
endif

set nv = ( `3dnvals -all $fname` )

3dTstat -tdiff -stdev -prefix __junk1.1D ${fname}\' >& /dev/null

set stat = 0
if ( $nv[4] > 1 ) then
  3dTstat -sos -prefix __junk2.1D __junk1.1D\'    >& /dev/null
  1deval -a __junk2.1D -expr 'sqrt(a)' 
  set stat = $status
else
  1dcat __junk1.1D
  set stat = $status
endif
/bin/rm -f __junk?.1D

exit $stat