NAME

       ncflint - netCDF File Interpolator

SYNTAX

       ncflint  [-3]  [-4] [-6] [-7] [-A] [--bfr sz][-C][-c][-D dbg_lvl] [-d dim,[ min][,[ max]]]
       [-F] [--fix_rec_crd]  [-G  gpe_dsc]  [-g  grp[,...]]   [-h]  [--hdf]  [--hdr_pad  sz]  [-i
       var,val3][-L  dfl_lvl][-l path] [--msa] [--no_tmp_fl] [-O] [-p path] [-R] [-r] [--ram_all]
       [-t thr_nbr] [--unn] [-v var[,...]]  [-w wgt[, wgt2]] [-X box] [-x] file1 file2 file3

DESCRIPTION

       ncflint creates an output file that is a linear combination  of  the  input  files.   This
       linear  combination  can  be  a  weighted  average,  a  normalized weighted average, or an
       interpolation of the input files.  Coordinate variables are not acted upon  in  any  case,
       they are simply copied from file_1.
        There  are  two  conceptually  distinct methods of using ncflint.  The first method is to
       specify the weight each input file is to have in the output file.   In  this  method,  the
       value  val3 of a variable in the output file file_3 is determined from its values val1 and
       val2 in the two input files according to wgt1*val1+wgt2*val2

       Here at least wgt1, and, optionally, wgt2, are specified on the command line with  the  -w
       (or  --weight  or  --wgt_var  )  switch.   If  only  IR  wgt1  is  specified  then wgt2 is
       automatically computed as wgt2=1-wgt1.  Note that weights larger than 1 are allowed.  Thus
       it  is possible to specify wgt1=2 and wgt2=-3.  One can use this functionality to multiply
       all the values in a given file by a constant.

       The second method of using ncflint is to specify the interpolation option with -i (or with
       the  --ntp  or --interpolate long options). This is really the inverse of the first method
       in the following sense.  When the user specifies the weights directly, ncflint has no work
       to  do  besides  multiplying  the  input values by their respective weights and adding the
       results together to produce the output values.  This assumes it is the  weights  that  are
       known  a  priori.   In another class of cases it is the "arrival value" (i.e., val3 ) of a
       particular variable var that is known a priori.  In this case,  the  implied  weights  can
       always be inferred by examining the values of var in the input files.  This results in one
       equation in two unknowns, wgt1 and wgt2: val3=wgt1*val1+wgt2*val2.

       Unique determination of  the  weights  requires  imposing  the  additional  constraint  of
       normalization  on  the  weights:  wgt1+wgt2=1.  Thus, to use the interpolation option, the
       user specifies var and val3 with the -i option.  ncflint will compute wgt1 and  wgt2,  and
       use these weights on all variables to generate the output file.  Although var may have any
       number of dimensions in the input files, it must represent a single, scalar  value.   Thus
       any dimensions associated with var must be "degenerate", i.e., of size one.

        If neither -i nor -w is specified on the command line, ncflint defaults to weighting each
       input file equally in the  output  file.   This  is  equivalent  to  specifying  -w0.5  or
       -w0.5,0.5.   Attempting  to  specify  both .BR -i and -w methods in the same command is an
       error.

       ncflint is programmed not to interpolate variables of  type  NC_CHAR  and  NC_BYTE.   This
       behavior is hardcoded.

AUTHOR

       NCO manual pages written by Charlie Zender and originally formatted by Brian Mays.

REPORTING BUGS

       Report bugs to <http://sf.net/bugs/?group_id=3331>.

COPYRIGHT

       Copyright © 1995-2010 Charlie Zender
       This  is  free software; see the source for copying conditions.  There is NO warranty; not
       even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

SEE ALSO

       The full documentation for NCO is maintained as a Texinfo manual  called  the  NCO  User's
       Guide.   Because  NCO  is mathematical in nature, the documentation includes TeX-intensive
       portions  not  viewable  on  character-based  displays.   Hence  the  only  complete   and
       authoritative  versions  of  the  NCO  User's  Guide  are  the PDF (recommended), DVI, and
       Postscript  versions  at  <http://nco.sf.net/nco.pdf>,  <http://nco.sf.net/nco.dvi>,   and
       <http://nco.sf.net/nco.ps>,   respectively.   HTML  and  XML  versions  are  available  at
       <http://nco.sf.net/nco.html> and <http://nco.sf.net/nco.xml>, respectively.

       If the info and NCO programs are properly installed at your site, the command

              info nco

       should give you access to the complete manual, except for the TeX-intensive portions.

HOMEPAGE

       The NCO homepage at <http://nco.sf.net> contains more information.

                                                                                       NCFLINT(1)