NAME
ncflint - netCDF File Interpolator
SYNTAX
ncflint [-3] [-4] [-6] [-A] [-C] [-c] [-D dbg] [-d dim,[ min][,[ max]]]
[-F] [-h] [-i var,val3][-L dfl_lvl][-l path] [-O] [-p path] [-R] [-r]
[-t thr_nbr] [-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 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.