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<title>GrADS Command: skip</title>
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<h2><b>skip()</b></h2>
<p>
<code>skip (<i>expr, skipi, skipj</i>)</code>
<p>
Sets alternating values of <code><i>expr</i></code> to the missing
data value.
<p>
<ul>
<code><i>expr</i> </code>A valid grid expression that may have 1 or 2 varying dimensions<br>
<code><i>skipi</i> </code>Skip factor in the I dimension of <code><i>expr</i></code><br>
<code><i>skipj</i> </code>Skip factor in the J dimension of <code><i>expr</i></code><br>
</ul>
<p>
<H3>Usage Notes</H3>
<P>
<ol>
<li>This function is often used while displaying wind <code>arrows</code> or <code>barbs</code> to thin the number of arrows or
barbs. It is not necessary to use the <code>skip</code> function on
both the U and V wind components; it is sufficient to populate only one
component with missing data values to suppress the plotting of the wind
<code>arrow</code> or <code>barb</code>.
</ol>
<p>
<h3>Examples </h3>
<ol>
<li>Suppose you have a time series of 3-hourly data, but you want to display values at 6-hourly time steps:<br>
<br><ul><code>set x 1<br>
set y 1<br>
set t 1 last<br>
d skip(var,2)</code><br>
</ul><br>
<li>To display every other grid point in both the X and Y direction:<br>
<br>
<ul>
<code>d skip(u,2,2);v</code>
</ul>
<br>
<li>To display every grid point in the Y direction, but every 5th grid
point in the X direction:<br>
<br>
<ul><code>d skip(u,5,1);v</code></ul>
<br>
<li>This example script "d_uv.gs" written by Wesley Ebisuzaki
automatically sets the skip factor based on the plot dimensions.
<br>
<pre>
*
* This function does a d skip(ugrd,n);v
* where n is automatically set to an appropriate value
*
* usage: d_uv ugrd vgrd
*
* v1.1 w. ebisuzaki
* v1.2 4/6/98 revised empirical formula for skip
*
function duv(arg)
u = subwrd(arg,1)
v = subwrd(arg,2)
* get lat/lon info
'query dims'
lons = sublin(result,2)
lats = sublin(result,3)
dx = subwrd(lons,13) - subwrd(lons,11)
dy = subwrd(lats,13) - subwrd(lats,11)
* Determine skip factor
dn = dx
if (dy > dx) ; dn = dy ; endif
skip = dn / 50 + 0.5
if (skip < 1) ; skip=1 ; endif
* Display the plot
'd skip('u','skip');'v
</pre>
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