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<!--Copyright (C) 1988-2005 by the Institute of Global Environment and Society (IGES). See file COPYRIGHT for more information.-->
<html>
<head>
<title>Displaying Data in GrADS</title>
</head>
<body bgcolor="e0f0ff" text="#000000">
<a href="#DDP">Drawing Data Plots</a><br>
<a href="#CTD">Clearing the Display</a><br>
<a href="#GOT">Graphics Output Types</a><br>
<a href="advdisplay.html">Advanced Display Options</a><br>
<p>
<hr>
<a name="DDP"><h2>Drawing Data Plots</h2></a>
The <code>display</code> command is how you actually display data (output
expressions) plots via the graphics output window. The command
is:<p>
<dd><code><a href="gradcomddisplay.html">display</a> <i>expression</i></code><p>
or<p>
<dd><code>d <i>expression</i></code><p>
The simplest <code><i>expression</i></code> is a variable abbreviation.<p>
If you display when <b>all</b> dimensions are fixed, you get a <b>single</b>
value which is typed out.<p>
If you display when <b>one</b> dimension varies, you get a <b>1-D line
graph</b> by default.<p>
If you display when <b>two</b> dimensions are varying, you get a <b>2-D
contour plot</b> by default.<p>
A variety of <a href="#GOT">plot types</a> are available in addition to the above
defaults.<p>
<a name="CTD"><h2>Clearing the Display</h2></a><p>
GrADS will overlay the output from each display command. To clear
the display, enter:<p>
<dd><code><a href="gradcomdclear.html">clear</a></code> (or just <code>c</code>)<p>
Issued without parameters, the <code>clear</code> command does pretty heavy
duty clearing of many of the GrADS internal settings. Parameters
can be added to limit what is cleared when using more advanced
features, for example:<p>
<ul>
<code>c events</code> flushes the events
buffer (e.g., mouse clicks)<br>
<code>c graphics</code> clears the graphics, but <b>not</b> the
widgets <br>
<code>c hbuff</code> clears
the display buffer when in double buffer mode</ul><p>
WARNING: If you make any error in the syntax of clear then
GrADS
does the full clear...<p>
<a name="GOT"><h2>Graphics Output Types</h2></a>
<p>
Before you can display a graph of your data, you will need to set
the type of plot you want and, probably, some other graphics
parameters as well.
<p>
By default, when one dimension varies, you get a line graph, and
when two dimensions vary, you get a contour plot. These defaults
can be changed by the command:
<p>
<ul>
<code>
<a href="gradcomdsetgxout.html">set gxout</a> <i>graphics_type</i>
</code>
</ul>
<p>
Some examples of <code><i>graphics_type</i></code> are <code>contour,
shaded, grid, bar, vector,</code> or <code>streamline</code>. For a
complete list, see the <a href="gradcomdsetgxout.html">reference
page</a>.
<p>
There are many options that can be set to control how the
data will be displayed for each <code><i>graphics_type</i></code>.
<p>
For the graphics output types <code>vector, stream,</code> and
<code>barb</code>, the plotting routines need two result grids, where the
first result grid is treated as the U component, and the second result
grid is treated as the V component. These two result grids are
provided to the <a href="gradcomddisplay.html">display</a> command by
entering two expressions separated by a semicolon:
<p>
<ul>
<code>
display u ; v<br>
display ave(u,t=1,t=10) ; ave(v,t=1,t=10)<br>
</code>
</ul>
<p>
For the graphics output types <code>vector</code> and
<code>stream</code>, you can specify a third result grid that will be used to
colorize the vectors or streamlines:
<p>
<ul>
<code>
display u ; v ; mag(u,v)<br>
display u ; v ; hcurl(u,v)<br>
</code>
</ul>
<p>
For a graphics output type <code>wxsym</code>, each value at a station
location is assumed to be a wx symbol code number. To see a chart of
all available wx symbols and their corresponding code numbers, run the
sample script <code>wxsym.gs</code>.
</body>
</html>
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