1NCRA(1)                     General Commands Manual                    NCRA(1)
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NAME

6       ncra - netCDF Record Averager
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SYNTAX

9       ncra  [-3] [-4] [-6] [-A] [-C] [-c] [-D dbg] [-d dim,[ min][,[ max]][,[
10       stride]]] [-F] [-h] [-L dfl_lvl] [-l path] [-n  loop]  [-O]  [-p  path]
11       [-R] [-r] [-t thr_nbr] [-v var[,...]]  [-X box] [-x] [-y op_typ] input-
12       files output-file
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DESCRIPTION

15       ncra averages record variables across  an  arbitrary  number  of  input
16       files.   The  record  dimension  is  retained  as a degenerate (size 1)
17       dimension in the output variables.
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19       Input files may vary in size, but each must have  a  record  dimension.
20       The  record  coordinate,  if any, should be monotonic for (or else non-
21       fatal warnings may be generated).  Hyperslabs of the  record  dimension
22       which  include more than one file are handled correctly.  ncra supports
23       the stride argument to the -d hyperslab option for the record dimension
24       only, stride is not supported for non-record dimensions.
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26       ncra weights each record (e.g., time slice) in the input-files equally.
27       ncra does not attempt to see if, say, the time  coordinate  is  irregu‐
28       larly spaced and thus would require a weighted average in order to be a
29       true time average.
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EXAMPLES

32       Average files 85.nc, 86.nc,  ...  89.nc along the record dimension, and
33       store the results in 8589.nc:
34              ncra 85.nc 86.nc 87.nc 88.nc 89.nc 8589.nc
35              ncra 8[56789].nc 8589.nc
36              ncra -n 5,2,1 85.nc 8589.nc
37       These three methods produce identical answers.
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39       Assume  the files 85.nc, 86.nc,  ...  89.nc each contain a record coor‐
40       dinate time of length 12 defined such that the third  record  in  86.nc
41       contains  data  from  March  1986, etc.  NCO knows how to hyperslab the
42       record dimension across files.  Thus, to average  data  from  December,
43       1985 through February, 1986:
44              ncra -d time,11,13 85.nc 86.nc 87.nc 8512_8602.nc
45              ncra -F -d time,12,14 85.nc 86.nc 87.nc 8512_8602.nc
46       The  file  87.nc  is  superfluous, but does not cause an error.  The -F
47       turns on the Fortran (1-based) indexing convention.  The following uses
48       the stride option to average all the March temperature data from multi‐
49       ple input files into a single output file
50              ncra  -F  -d  time,3,,12  -v  temperature  85.nc   86.nc   87.nc
51              858687_03.nc
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53       Assume the time coordinate is incrementally numbered such that January,
54       1985 = 1 and December, 1989 = 60.  Assuming ??   only  expands  to  the
55       five desired files, the following averages June, 1985--June, 1989:
56              ncra -d time,6.,54. ??.nc 8506_8906.nc
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AUTHOR

60       NCO manual pages written by Charlie Zender and Brian Mays.
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REPORTING BUGS

64       Report bugs to <http://sf.net/bugs/?group_id=3331>.
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68       Copyright © 1995-2010 Charlie Zender
69       This is free software; see the source for copying conditions.  There is
70       NO warranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR
71       PURPOSE.
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SEE ALSO

75       The full documentation for NCO is maintained as a Texinfo manual called
76       the NCO User's Guide.  Because NCO is mathematical in nature, the docu‐
77       mentation  includes  TeX-intensive  portions not viewable on character-
78       based displays.  Hence the only complete and authoritative versions  of
79       the  NCO  User's  Guide  are the PDF (recommended), DVI, and Postscript
80       versions at  <http://nco.sf.net/nco.pdf>,  <http://nco.sf.net/nco.dvi>,
81       and  <http://nco.sf.net/nco.ps>,  respectively.   HTML and XML versions
82       are      available      at       <http://nco.sf.net/nco.html>       and
83       <http://nco.sf.net/nco.xml>, respectively.
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85       If  the  info and NCO programs are properly installed at your site, the
86       command
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88              info nco
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90       should give you access to the complete  manual,  except  for  the  TeX-
91       intensive portions.
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HOMEPAGE

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