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Chapters:
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<a href="Introduction.html">1: Introduction</a><br>
<a href="SimpleExample.html">2: Simple example</a><br>
<a href="InvokingGri.html">3: Invocation</a><br>
<a href="GettingMoreControl.html">4: Finer Control</a><br>
<a href="X-Y.html">5: X-Y Plots</a><br>
<a href="ContourPlots.html">6: Contour Plots</a><br>
<a href="Images.html">7: Image Plots</a><br>
<a href="Examples.html">8: Examples</a><br>
<a href="Commands.html">9: Gri Commands</a><br>
<a href="Programming.html">10: Programming</a><br>
<a href="Environment.html">11: Environment</a><br>
<a href="Emacs.html">12: Emacs Mode</a><br>
<a href="History.html">13: History</a><br>
<a href="Installation.html">14: Installation</a><br>
<a href="Bugs.html">15: Gri Bugs</a><br>
<a href="TestSuite.html">16: Test Suite</a><br>
<a href="Acknowledgments.html">17: Acknowledgments</a><br>
<a href="License.html">18: License</a><br>
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Indices:</br>
<a href="ConceptIndex.html"><i>Concepts</i></a><br>
<a href="CommandIndex.html"><i>Commands</i></a><br>
<a href="BuiltinIndex.html"><i>Variables</i></a><br>
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<h3>10.9.7: Manipulation of Columns etc</h3>
<h4>10.9.7.1: Columns</h4>
<!-- latex: \index{@code{..num_col_data..}, number column data} -->
Individual data in the `<font color="#82140F"><code>x</code></font>', `<font color="#82140F"><code>y</code></font>', `<font color="#82140F"><code>z</code></font>', `<font color="#82140F"><code>u</code></font>', `<font color="#82140F"><code>v</code></font>'
and `<font color="#82140F"><code>weight</code></font>' columns can be accessed with the `<font color="#82140F"><code>@</code></font>' operator.
The first point has index 0. Examples:
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<PRE>
<font color="#82140F">
show "first x is " {rpn x 0 @ }
show "last x is " {rpn x ..num_col_data.. 1 - @ }
show "and here are all the data:"
.i. = 0
while {rpn .i. ..num_col_data.. >}
show {rpn x .i. @ }
.i. += 1
end while
</font></PRE>
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<p>
The mean value is available from the `<font color="#82140F"><code>mean</code></font>' operator (e.g.,
`<font color="#82140F"><code>.xmean. = {rpn x mean }</code></font>', while the standard deviation is given
by `<font color="#82140F"><code>stddev</code></font>' and the minimal and maximal values are given by
`<font color="#82140F"><code>min</code></font>' and `<font color="#82140F"><code>max</code></font>'.
<p>
The area under the curve y=y(x) is found by `<font color="#82140F"><code>{rpn y x area }</code></font>',
defined by
`<font color="#82140F"><code>0.5 * sum ( (y[i] + y[i-1]) * (x[i] - x[i-1]) )</code></font>'
for `<font color="#82140F"><code>i</code></font>' ranging from 1 to `<font color="#82140F"><code>..num_col_data..</code></font>'-1.
<p>
<h4>10.9.7.2: Grid</h4>
Grid data can be accessed with e.g. `<font color="#82140F"><code>{rpn grid min } </code></font>',
`<font color="#82140F"><code>{rpn grid max } </code></font>', and `<font color="#82140F"><code>{rpn grid mean } </code></font>'.
<p>
The value of the grid at a given `<font color="#82140F"><code>(.x.,.y.)</code></font>' coordinate may be
found by by e.g. `<font color="#82140F"><code>{rpn grid .x. .y. interpolate}</code></font>'. The
interpolation scheme is the same as that used in converting grids to
images.
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