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<br>
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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<h2>4.2: Axis scaling</h2>
<!-- latex: \index{@code{..xlast..}, last drawn x value} -->
<!-- latex: \index{@code{..ylast..}, last drawn y value} -->
<!-- latex: \index{@code{..xmargin..}, left margin} -->
<!-- latex: \index{@code{..ymargin..}, bottom margin} -->
<!-- latex: \index{@code{..xsize..}, x-axis length} -->
<!-- latex: \index{@code{..ysize..}, y-axis length} -->
<!-- latex: \index{@code{..xleft..}, x value at left of plot} -->
<!-- latex: \index{@code{..xright..}, x value at right of plot} -->
<!-- latex: \index{@code{..ybottom..}, y value at bottom of plot} -->
<!-- latex: \index{@code{..ytop..}, y value at top of plot} -->
Gri normally assumes that you are plotting scientific graphs, and
therefore whenever it sees a command like `<font color="#82140F"><code>draw curve</code></font>' or
`<font color="#82140F"><code>draw symbol</code></font>', it draws an appropriate axis first. You can turn
this feature off, by using `<font color="#82140F"><code>draw axes none</code></font>' before the other
`<font color="#82140F"><code>draw</code></font>' command.
<p>
Furthermore, Gri picks axis scales by itself, by scanning the (`<font color="#82140F"><code>x</code></font>',
`<font color="#82140F"><code>y</code></font>') columns. If you don't like the scales Gri picks, you can
override them (see <a href="AxisRange.html#Range">Range</a>).
<p>
Gri normally draws axes labelled at left and bottom, and with an axis
frame with tics all around. If you don't like this default axis style
you can specify other styles. For example, if the commands
`<font color="#82140F"><code>draw x axis</code></font>' and `<font color="#82140F"><code>draw y axis</code></font>' are placed before the `<font color="#82140F"><code>draw curve</code></font>'
command, Gri will realize you've already specified axes, and just draw
them on the left and bottom sides of the box, without completing the
axis frame.
<p>
For your general use, Gri stores the minimum and maximum x and y values
of the <b>axes</b> in the variables `<font color="#82140F"><code>..xleft..</code></font>', `<font color="#82140F"><code>..xright..</code></font>',
`<font color="#82140F"><code>..ybottom..</code></font>', and `<font color="#82140F"><code>..ytop..</code></font>'; for the minimum and maximum
values of the <b>data</b>, use the built-in rpnfunctions `<font color="#82140F"><code>min</code></font>',
`<font color="82140F"><code>max</code></font>', and `<font color="#82140F"><code>mean</code></font>' (see <a href="Rpnfunction.html#Rpnfunction">Rpnfunction</a>). It stores the last
(x,y) pair on a curve (whether data or axis) as
(`<font color="#82140F"><code>..xlast..</code></font>',`<font color="#82140F"><code>..ylast..</code></font>'). Also, Gri stores the axis sizes in
`<font color="#82140F"><code>..xsize..</code></font>' and `<font color="#82140F"><code>..ysize..</code></font>'. It stores the space to the left
of the plot in `<font color="#82140F"><code>..xmargin..</code></font>' and the space below the plot in
`<font color="#82140F"><code>..ymargin..</code></font>'.
<p>
The axis scales are <b>not</b> changed by mathematical operations on the
columns, regardless of whether the scales were set manually (by a
`<font color="#82140F"><code>set x|y axis</code></font>' command), or by Gri (during a `<font color="#82140F"><code>read columns</code></font>'
command). In the former case, this is what you probably want, but in
the latter case it can lead to graphs with no data, because the scale
does not apply to the transformed data. This might be considered a bug;
in any case, you can avoid it by transforming the built-in variables
`<font color="#82140F"><code>..xleft..</code></font>' and `<font color="#82140F"><code>..xright..</code></font>' whenever you transform the x
column, and `<font color="#82140F"><code>..ybottom..</code></font>' and `<font color="#82140F"><code>..ytop..</code></font>' whenever you
transform the y column.
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