r.describe

NAME

r.describe - Prints terse list of category values found in a raster map layer.
(GRASS Raster Program)

SYNOPSIS

r.describe
r.describe help
r.describe [-1rqd] map=name[nv=string][nsteps=value]

DESCRIPTION

r.describe prints a terse listing of category values found in a user-specified raster map layer.

OPTIONS

The program will be run non-interactively, if the user specifies the name of a raster map layer and any desired flags on the command line, using the form

r.describe [-1rqd] map=name

where the map name is the name of a raster map layer whose categories are to be described, and the (optional) flags -1, -r, -q, and -d have the meanings described below.

Alternately, the user can simply type r.describe on the command line, without program arguments. In this case, the user will be prompted for needed flag settings and the parameter value using the standard GRASS parser.

PROGRAM USE

The user can select one of the following two output reports from r.describe:

(1) RANGE.

A range of category values found in the raster map layer will be printed. The range is divided into three groups: negative, positive, and zero. If negative values occur, the minimum and maximum negative values will be printed. If positive values occur, the minimum and maximum positive values will be printed. If zero occurs, this will be indicated.

(2) FULL LIST.

A list of all category values that were found in the raster map layer will be printed.

The following sample output from r.describe:

0 2-4 10-13

means that category data values 0, 2 through 4, and 10 through 13 occurred in the named map layer.

The user must choose to read the map layer in one of two ways:

(1) DIRECTLY.: The current geographic region and mask are ignored and the full raster map layer is read. This method is useful if the user intends to reclassify or rescale the data, since these functions (r.reclass and r.rescale) also ignore the current geographic region and mask.
(2) REGIONED and MASKED.: The map layer is read within the current geographic region, masked by the current mask.

NON-INTERACTIVE PROGRAM USE

r.describe examines a user-chosen raster map layer. If run non-interactively, the layer name must be supplied on the command line.

A compact list of category values that were found in the data layer will be printed.

Following is a sample output:

0 2-4 10-13

Flags:

-l

Print the output one value per line, instead of the default short form. In the above example, the -1 option would output:

-r

Only print the range of the data. The highest and lowest positive values, and the highest and lowest negative values, are output. In the above example, the -r option would output:

0 2 13

If the -1 option is also specified, the output appears with one category value per line.

-q

Quiet. The -q option will tell r.describe to be silent while reading the raster file. If not specified, program percentage-completed messages are printed.

-d

Use the current geographic region settings. Normally, r.describe will read the data layer directly, ignoring both the current region settings and mask. The -d option tells r.describe to read the map layer in the current region masked by the current mask (if any).

Parameters:

map=name: Name of raster map.
nv=string: String representing no data cell value.
nsteps=value: Number of quantization steps.

NOTES

The range report will generally run faster than the full list.

AUTHOR

Michael Shapiro, U.S. Army Construction Engineering Research Laboratory