free grads

query

The query command allows the user to get information about a variety of aspects of the current grads session. Configuration, plot characteristics, graphics specifics, and file structure are some examples. The use of query pos combined with the coordinate transformations is the basis of many interactive applications with buttons and drop menus. The query command may be shortened to simply q. The syntax is:  

set xyrev

set xyrev on|off

Reverses the axes on a plot. 

set xsize

Resizes the window to x,y pixels. 

set xlpos

set xlpos offset side

Controls position of x axis labels

set xlopts

This command controls the appearance of the tic labels on the X axis. 

set xlint

set xlint interval

Specifies the interval between labeled tick marks on the X-axis.   

set xlevs

set xlevs lev1 lev2 ... levN

Allows the user to specify each individual labeled tick mark for the X-axis.  

set xlabs

label the x axis with lab1, lab2, lab3,...

set xlab

set xlab option

Controls the format of X-axis tick mark labels. The option argument may be one of the following:  

draw xlab

draw xlab string

Writes string in an appropriate position to label x axis.

set xflip

set xflip on|off

Flips the order of the horizontal axis (whatever axis is horizontal after xyrev is applied). Reset by a clear or set vpage command.

xdfopen

xdfopen filename

grads requires a certain amount of metadata in order to understand how to read a NetCDF/HDF-SDS data file, also called a self-describing file (SDF). The sdfopen command assumes all the metadata is internal to the self-describing file, whereas the xdfopen command allows the user to supplement or replace any internal metadata via a data descriptor file. In this way, xdfopen provides access to some self-describing files that do not comply with the COARDS conventions.

filename is the name of the data descriptor file that contains the supplemental metadata. It has a syntax very similar to the regular data descriptor files that are used with the open command. The few differences are noted below:  

set xaxis

set xaxis start end <increment>

set x|y|z|t|e

set x|y|z|t|e val1 <val2>

This sets one dimension of the dimension environment using grid coordinates. You may use whatever coordinates are convenient to you. Issuing set lon is equivalent to issuing set x, both set the x dimension. The difference is only the units you wish to use when entering the command.

When you enter just one value, that dimension is said to be "fixed". When you enter two values, that dimension is said to be "varying". The combination of fixed and varying dimensions defines the dimension environment.