1NCRA(1) General Commands Manual NCRA(1)
2
6 ncra - netCDF Record Averager
7
9 ncra [-A] [-C] [-c] [-D dbg] [-d dim,[ min][,[ max]][,[ stride]]] [-F]
10 [-h] [-l path] [-n loop] [-O] [-p path] [-R] [-r] [-v var[,...]] [-x]
11 [-y op_typ] input-files output-file
12
14 ncra averages record variables across an arbitrary number of input
15 files. The record dimension is retained as a degenerate (size 1)
16 dimension in the output variables.
17 Input files may vary in size, but each must have a record dimension.
19 The record coordinate, if any, should be monotonic for (or else non-
20 fatal warnings may be generated). Hyperslabs of the record dimension
21 which include more than one file are handled correctly. ncra supports
22 the stride argument to the -d hyperslab option for the record dimension
23 only, stride is not supported for non-record dimensions.
24 ncra weights each record (e.g., time slice) in the input-files equally.
26 ncra does not attempt to see if, say, the time coordinate is irregu‐
27 larly spaced and thus would require a weighted average in order to be a
28 true time average.
29
31 Average files 85.nc, 86.nc, 89.nc along the record dimension, and store
32 the results in 8589.nc:
33 ncra 85.nc 86.nc 87.nc 88.nc 89.nc 8589.nc
34 ncra 8[56789].nc 8589.nc
35 ncra -n 5,2,1 85.nc 8589.nc
36 These three methods produce identical answers.
37 Assume the files 85.nc, 86.nc, 89.nc each contain a record coordinate
39 time of length 12 defined such that the third record in 86.nc contains
40 data from March 1986, etc. NCO knows how to hyperslab the record
41 dimension across files. Thus, to average data from December, 1985
42 through February, 1986:
43 ncra -d time,11,13 85.nc 86.nc 87.nc 8512_8602.nc
44 ncra -F -d time,12,14 85.nc 86.nc 87.nc 8512_8602.nc
45 The file 87.nc is superfluous, but does not cause an error. The -F
46 turns on the Fortran (1-based) indexing convention. The following uses
47 the stride option to average all the March temperature data from multi‐
48 ple input files into a single output file
49 ncra -F -d time,3,,12 -v temperature 85.nc 86.nc 87.nc
50 858687_03.nc
51 Assume the time coordinate is incrementally numbered such that January,
53 1985 = 1 and December, 1989 = 60. Assuming ?? only expands to the
54 five desired files, the following averages June, 1985--June, 1989:
55 ncra -d time,6.,54. ??.nc 8506_8906.nc
56
59 NCO manual pages written by Charlie Zender and Brian Mays.
60
63 Report bugs to <http://sf.net/bugs/?group_id=3331>.
64
67 Copyright © 1995-2004 Charlie Zender
68 This is free software; see the source for copying conditions. There is
69 NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR
70 PURPOSE.
71
74 The full documentation for NCO is maintained as a Texinfo manual called
75 the NCO User's Guide. Because NCO is mathematical in nature, the docu‐
76 mentation includes TeX-intensive portions not viewable on character-
77 based displays. Hence the only complete and authoritative versions of
78 the NCO User's Guide are the PDF (recommended), DVI, and Postscript
79 versions at <http://nco.sf.net/nco.pdf>, <http://nco.sf.net/nco.dvi>,
80 and <http://nco.sf.net/nco.ps>, respectively. HTML and XML versions
81 are available at <http://nco.sf.net/nco.html> and
82 <http://nco.sf.net/nco.xml>, respectively.
83 If the info and NCO programs are properly installed at your site, the
85 command
86 info nco
88 should give you access to the complete manual, except for the TeX-
90 intensive portions.
91
94 The NCO homepage at <http://nco.sf.net> contains more information.
95 NCRA(1)