IFILTER(1)

IFILTER

     module - Temporal two-point filtering of intensity images.

SYNOPSIS

     ifilter [-qv] in=dataset out=dataset [in2=dataset RATIO=n]

DESCRIPTION

     ifilter  performs  two-point  filtering  of  intensity   (or
     rotation-corrected  velocity?)  images.   The  nth  filtered
     image is

           out[n] = (in[n+1] - in[n])

          or, if RATIO=1,

           out[n] = (in[n+1] - in[n]) / in[n]

     ifilter can be called with one or more in datasets, an equal
     number  of  out  datasets, and an optional in2 dataset.  The
     in2 dataset is used to filter the last image of the last  in
     dataset.   Due  to  the  two-point nature of the filter, the
     number of images in the out dataset will be

          nout = nin - ngaps

     where nin is the number of images in the in  dataset,  ngaps
     is  the  number of gaps in the data, and the end of all data
     should be considered as a gap.  That is, in a 'perfect' col-
     lection of images, nout = nin - 1.

     The -q option prints out the list of required arguments  and
     their  default  or environmental values, then quits.  The -v
     option sets verbose mode, redirecting history from stdout to
     stderr.

OPTIONS

     in=Dataset_Name     No default

     out=Dataset_Name    No default

     in2=Dataset_Name    Default: NOT SPECIFIED

     RATIO=Boolean       Default: 0 (false)

EXAMPLES

     ifilter               -v                                   \
          in=prog:hlh_sp,level:lev2,series:90_91[0]             \
          in2=prog:hlh_sp,level:lev2,series:90_91[1]            \
          out=prog:hlh_sp,level:lev2_filt,series:90_91[]        \
          RATIO=1


     ifilter               -v                                   \
          in=prog:hlh_sp,level:lev2,series:90_91[0-6]           \
          out=prog:hlh_sp,level:lev2_filt,series:90_91[]

     ifilter               -v                                   \
          in=prog:hlh_sp,level:lev2,series:90_91[0-6]           \
          in2=prog:hlh_sp,level:lev2,series:90_91[7]            \
          out=prog:hlh_sp,level:lev2_filt,series:90_91[]

FILES

     none

SEE ALSO

DIAGNOSTICS

BUGS

     Don't try this with any thing but floating-point data.

     Also, when running in the pipeline it is  probably  best  to
     specify in2 even if it is something stupid, like this:

     ifilter               -v                                   \
          in=prog:hlh_sp,level:lev2,series:90_91[0-6]           \
          in2=prog:hlh_sp,level:lev2,series:90_91[6]            \
          out=prog:hlh_sp,level:lev2_filt,series:90_91[]

     Not specifying in2 can result in an abort (but it works fine
     outside pe).

AUTHOR

     Peter Giles         giles@quake.stanford.edu

HISTORY

     Created Nov/95.