MINMAX(l) MINMAX(l)
NAME
minmax - Find extreme values in data tables
SYNOPSIS
minmax [ files] [ -C ] [ -D ] [ -H[nrec] ] [ -Idx[/dy] ] [ -L ] [ -M[flag] ] [ -: ] [ -bi[s][n] ]
DESCRIPTION
minmax reads its standard input [or from files] and finds the extreme values in each of the columns. It recognizes NaNs and will print
warnings if the number of columns vary from record to record. As an option, minmax will find the extent of the first two columns rounded
up and down to the nearest multiple of dx/dy. This output will be in the form -Rw/e/s/n which can be used directly in the command line for
other programs, or simply in column form.
xyzfile
ASCII [or binary, see -b] file(s) holding a fixed number of data columns.
OPTIONS -C Report the min/max values per column in separate columns [Default uses <min/max> format]
-D Sets longitude discontinuity to the Dateline (-180/+180) [Default is Greenwich (0-360)]. Requires -L.
-H Input file(s) has Header record(s). Number of header records can be changed by editing your .gmtdefaults file. If used, GMT default
is 1 header record.
-I Report the min/max of the first two columns to the nearest multiple of dx and dy, and output this in the form -Rw/e/s/n (unless -C
is set).
-L Indicates that the x column contains longitudes, which may be periodic in 360 degrees [Default assumes no periodicity].
-M Multiple segment file(s). Segments are separated by a special record. For ASCII files the first character must be flag [Default is
'>']. For binary files all fields must be NaN.
-: Toggles between (longitude,latitude) and (latitude,longitude) input/output. [Default is (longitude,latitude)]. Applies to geo-
graphic coordinates only. Only works when -I is selected.
-bi Selects binary input. Append s for single precision [Default is double]. Append n for the number of columns in the binary file(s).
[Default is 2 input columns].
EXAMPLES
To find the extreme values in the file ship_gravity.xygd, try
minmax ship_gravity.xygd
Output should look like
ship_gravity.xygd: N = 6992 <326.125/334.684> <-28.0711/-8.6837> <-47.7/177.6> <0.6/3544.9>
To find the extreme values in the file track.xy to the nearest 5 units and use this region to draw a line using psxy, try
psxy `minmax -I5 track.xy` track.xy -Jx1 -B5 -P > track.ps
To find the min and max values for each column, but rounded to integers, try
minmax junkfile -C -I1
SEE ALSO gmt(1gmt)
1 Jan 2004 MINMAX(l)
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BLOCKMEAN(l) BLOCKMEAN(l)
NAME
blockmean - filter to block average (x,y,z) data by L2 norm
SYNOPSIS
blockmean [ xyz[w]file(s) ] -Ix_inc[m|c][/y_inc[m|c]] -Rwest/east/south/north[r] [ -C ] [ -F ] [ -H[nrec] ] [ -L ] [ -S ] [ -V ] [ -W[io] ]
[ -: ] [ -bi[s][n] ] [ -bo[s][n] ]
DESCRIPTION
blockmean reads arbitrarily located (x,y,z) triples [or optionally weighted quadruples (x,y,z,w)] from standard input [or xyz[w]file(s)]
and writes to standard output a mean position and value for every non-empty block in a grid region defined by the -R and -I arguments.
Either blockmean, blockmedian, or blockmode should be used as a pre-processor before running surface to avoid aliasing short wavelengths.
These routines are also generally useful for decimating or averaging (x,y,z) data. You can modify the precision of the output format by
editing the D_FORMAT parameter in your .gmtdefaults file, or you may choose binary input and/or output using single or double precision
storage.
xyz[w]file(s)
3 [or 4] column ASCII file(s) [or binary, see -b] holding (x,y,z[,w]) data values. [w] is an optional weight for the data. If no
file is specified, blockmean will read from standard input.
-I x_inc [and optionally y_inc] is the grid spacing. Append m to indicate minutes or c to indicate seconds.
-R west, east, south, and north specify the Region of interest. To specify boundaries in degrees and minutes [and seconds], use the
dd:mm[:ss] format. Append r if lower left and upper right map coordinates are given instead of wesn.
OPTIONS -C Use the center of the block as the output location [Default uses the mean location].
-F Block centers have pixel registration. [Default: grid registration.] (Registrations are defined in GMT Cookbook Appendix B on grid
file formats.) Each block is the locus of points nearest the grid value location. For example, with -R10/15/10/15 and and -I1: with
the -F option 10 <= (x,y) < 11 is one of 25 blocks; without it 9.5 <= (x,y) < 10.5 is one of 36 blocks.
-H Input file(s) has Header record(s). Number of header records can be changed by editing your .gmtdefaults file. If used, GMT default
is 1 header record. Not used with binary data.
-L Indicates that the x column contains longitudes, which may differ from the region in -R by [multiples of] 360 degrees [Default
assumes no periodicity].
-S Report the sum of all z-values inside a block [Default reports mean value].
-V Selects verbose mode, which will send progress reports to stderr [Default runs "silently"].
-W Weighted modifier[s]. Unweighted input and output has 3 columns x,y,z; Weighted i/o has 4 columns x,y,z,w. Weights can be used in
input to construct weighted mean values in blocks. Weight sums can be reported in output for later combining several runs, etc. Use
-W for weighted i/o, -Wi for weighted input only, -Wo for weighted output only. [Default uses unweighted i/o]
-: Toggles between (longitude,latitude) and (latitude,longitude) input/output. [Default is (longitude,latitude)]. Applies to geo-
graphic coordinates only.
-bi Selects binary input. Append s for single precision [Default is double]. Append n for the number of columns in the binary file(s).
[Default is 3 (or 4 if -W is set)].
-bo Selects binary output. Append s for single precision [Default is double].
EXAMPLES
To find 5 by 5 minute block means from the ASCII data in hawaii.xyg, try
blockmean hawaii.xyg -R198/208/18/25 -I5m > hawaii_5x5.xyg
SEE ALSO blockmedian(1gmt), blockmode(1gmt), gmtdefaults(1gmt), gmt(1gmt), nearneighbor(1gmt), surface(1gmt), triangulate(1gmt)
1 Jan 2004 BLOCKMEAN(l)