GrADS commands are entered in the terminal window and the response from GrADS is either graphics in the graphics window or text in the terminal window. The three fundamental GrADS commands:
open open or make available to GrADS a data file
with
either gridded or station data
d display a GrADS
"expression" (e.g., a slice of data)
set manipulate the "what" "where" and
"how" of data
display
The GrADS "expression," or what you want to look at, can be as
simple as a variable in the data file that was opened, e.g., d
slp or an arithmetic or GrADS function operation on the data,
e.g., d slp/100 or d mag(u,v) where mag is a GrADS intrinsic
function.
The "where" of data display is called the "dimension environment"
and defines which part, chunk or "hyperslab" of the 4-D
geophysical space (lon,lat,level,time) is displayed. The
dimension environment is manipulated through the set command and
is controlled in either grid coordinates (x,y,z,t or indices) or
world coordinates (lon, lat,lev, time).
The "what" and "how" of display is controlled by set
commands and
includes both graphics methods (e.g., contours, streamlines) and
data (e.g., d to a file).
GrADS graphics can be written to a file (i.e., enable print
filename and print)
and then converted to postscript for
printing
and/or conversion to other image formats.
In addition, GrADS includes graphic primitives (e.g., lines and
circles) and basic labelling through the draw
command.
The q or query
command is used to get information from GrADS
such
as which files are opened and even statistics.