grdclipgmt - Online in the Cloud

PROGRAM:

NAME

grdclip - Clip the range of grids

SYNOPSIS

grdclip ingrid outgrid [ region ] [ ahigh/above ] [ blow/below ] [ ilow/high/between ] [
rold/new ] [ [level] ]

Note: No space is allowed between the option flag and the associated arguments.

DESCRIPTION

grdclip will set values < low to below and/or values > high to above. You can also specify
one or more intervals where all values should be set to IT(between), or replace individual
values. Such operations are useful when you want all of a continent or an ocean to fall
into one color or gray shade in image processing, when clipping of the range of data
values is required, or for reclassification of data values. above, below, between, old
and new can be any number or even NaN (Not a Number). You must choose at least one of the
-S options. Use -R to only extract a subset of the ingrid file.

REQUIRED ARGUMENTS

ingrid The input 2-D binary grid file.

-Goutgrid
outgrid is the modified output grid file.

OPTIONAL ARGUMENTS

-R[unit]xmin/xmax/ymin/ymax[r] (more ...)
Specify the region of interest. Using the -R option will select a subsection of
ingrid grid. If this subsection exceeds the boundaries of the grid, only the common
region will be extracted.

-Sahigh/above
Set all data[i] > high to above.

-Sblow/below
Set all data[i] < low to below.

-Silow/high/between
Set all data[i] >= low and <= high to between. Repeat the option for as many
intervals as are needed.

-Srold/new
Set all data[i] == old to new. This is mostly useful when your data are known to
be integer values. Repeat the option for as many replacements as are needed.

-V[level] (more ...)
Select verbosity level [c].

-^ or just -
Print a short message about the syntax of the command, then exits (NOTE: on Windows
use just -).

-+ or just +
Print an extensive usage (help) message, including the explanation of any
module-specific option (but not the GMT common options), then exits.

-? or no arguments
Print a complete usage (help) message, including the explanation of options, then
exits.

--version
Print GMT version and exit.

--show-datadir
Print full path to GMT share directory and exit.

GRID FILE FORMATS

By default GMT writes out grid as single precision floats in a COARDS-complaint netCDF
file format. However, GMT is able to produce grid files in many other commonly used grid
file formats and also facilitates so called "packing" of grids, writing out floating point
data as 1- or 2-byte integers. To specify the precision, scale and offset, the user should
add the suffix =id[/scale/offset[/nan]], where id is a two-letter identifier of the grid
type and precision, and scale and offset are optional scale factor and offset to be
applied to all grid values, and nan is the value used to indicate missing data. In case
the two characters id is not provided, as in =/scale than a id=nf is assumed. When
reading grids, the format is generally automatically recognized. If not, the same suffix
can be added to input grid file names. See grdconvert and Section grid-file-format of the
GMT Technical Reference and Cookbook for more information.

When reading a netCDF file that contains multiple grids, GMT will read, by default, the
first 2-dimensional grid that can find in that file. To coax GMT into reading another
multi-dimensional variable in the grid file, append ?varname to the file name, where
varname is the name of the variable. Note that you may need to escape the special meaning
of ? in your shell program by putting a backslash in front of it, or by placing the
filename and suffix between quotes or double quotes. The ?varname suffix can also be used
for output grids to specify a variable name different from the default: "z". See
grdconvert and Sections modifiers-for-CF and grid-file-format of the GMT Technical
Reference and Cookbook for more information, particularly on how to read splices of 3-,
4-, or 5-dimensional grids.

EXAMPLES

To set all values > 70 to NaN and all values < 0 to 0 in file data.nc:

gmt grdclip data.nc -Gnew_data.nc -Sa70/NaN -Sb0/0 -V

To reclassify all values in the 25-30 range to 99, those in 35-39 to 55, exchange 17 for
11 and all values < 10 to 0 in file classes.nc, try

gmt grdclip classes.nc -Gnew_classes.nc -Si25/30/99 -Si35/39/55 -Sr17/11 -Sb10/0 -V

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