147 lines
16 KiB
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147 lines
16 KiB
HTML
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<html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8"><title>Rotating graphs</title><link rel="stylesheet" type="text/css" href="manual.css"><meta name="generator" content="DocBook XSL Stylesheets V1.76.0"><link rel="home" href="index.html" title="JpGraph Manual"><link rel="up" href="ch14.html" title="Chapter 14. Common features for all Cartesian (x,y) graph types"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Rotating graphs</th></tr><tr><td width="20%" align="left"> </td><th width="60%" align="center">Chapter 14. Common features for all Cartesian (x,y) graph types</th><td width="20%" align="right"> </td></tr></table><hr></div><div class="sect1" title="Rotating graphs"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="id2548593"></a>Rotating graphs</h2></div></div></div>
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<p>The library supports an arbitrary rotation of a the plot area as well as some
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special convenience method to rotate the plot area 90 degree which most often is
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used to draw a horizontal bar graph instead of a (standard) vertical bar
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graph.</p>
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<p>
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</p><div class="caution" title="Caution" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Caution</h3>
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<p>Adding a rotation transformation will make the graph generation slightly
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slower since each point of the graph as to go through a transformation step
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before being stroked on to the image. The library tries to mitigate this as
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much as possible by using a pre-calculated transformation matrix and also
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makes further optimizations for the special case of 90 degree
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rotations.</p>
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</div><p>
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</p>
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<p>
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</p><div class="caution" title="Caution" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Caution</h3>
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<p>Any background images (see <a class="xref" href="ch14s15.html" title="Adding images and country flags to the background of the graph">Adding images and country flags to the background of the graph</a>) will not be rotated with the graph. This limitation exists since the
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performance and memory usage of doing real image transformation in PHP would
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be too poor. Any background images needing rotation must be rotated outside
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in some image manipulation program (e.g. Gimp, IrfanView).</p>
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</div><p>
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</p>
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<p>When a plot area is rotated there are two things to be aware of </p>
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<p>
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</p><div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
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<p><span class="italic">individual labels on the axis are not
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rotated</span></p>
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<p>The design decision behind this is that bit mapped fonts cannot be
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arbitrarily rotated and rotating TTF fonts will decrease (in general)
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the readability. If angle rotation is needed on the labels it is still
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possible to use the method <code class="code">Axis::SetLabelAngle()</code></p>
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<p>
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</p><div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
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<p>Since the anchor point for labels is by default the optimum
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for graph at 0 degree the anchor point and alignment for the
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labels on the axis should probably be adjusted to get a better
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visual appearance on the rotated graph. This is accomplished by
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the method <code class="code">Axis::SetLabelAlign()</code>
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</p>
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</div><p>
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</p>
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</li><li class="listitem">
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<p><span class="italic">any background image or background gradient is
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not rotated</span></p>
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<p>The design decision behind this is purely computational Doing a full
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image rotation would be excruciating CPU intensive using PHP.</p>
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</li></ol></div><p>
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</p>
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<div class="sect2" title="Free rotation of the plot area"><div class="titlepage"><div><div><h3 class="title"><a name="id2551329"></a>Free rotation of the plot area</h3></div></div></div>
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<p>The rotation of the plot area is controlled with the following two methods </p>
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<p>
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</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
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<p><code class="code">Image::SetAngle($aAngle)</code></p>
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<p>"<code class="code">$Angle</code>" = Angle of rotation specified in degrees. A
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positive angle specifies a clockwise rotation.</p>
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</li><li class="listitem">
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<p><code class="code">Image::SetCenter($aX, $aY)</code></p>
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<p>Specifies the center of rotation</p>
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</li></ul></div><p>
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</p>
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<p>The Image class is the lowest graphic layer in the library and it is access
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through the instance variable "<code class="code">$img</code>" of the Graph class. So for
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example to rotate a plot are 45 degree the following line has to be added</p>
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<p>
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</p><div class="hl-main"><table class="hl-table" width="100%"><tr><td class="hl-gutter" align="right" valign="top"><pre>1
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</pre></td><td class="hl-main" valign="top"><pre><span class="hl-code">$graph->img->SetAngle(45);</span></pre></td></tr></table></div><p>
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</p>
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<p>By default the center of rotation will be the center point of the plot area.
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The following examples will clarify this. We will use the (very) basic graph
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shown in <a class="xref" href="ch14s12.html#fig.rotex0" title="Figure 14.74. Original unrotated graph (rotex0.php)">Figure 14.74. Original unrotated graph <code class="uri"><a class="uri" href="example_src/rotex0.html" target="_top">(<code class="filename">rotex0.php</code>)</a></code> </a> to demonstrate rotation.</p>
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<p>
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</p><div class="figure"><a name="fig.rotex0"></a><p class="title"><b>Figure 14.74. Original unrotated graph <code class="uri"><a class="uri" href="example_src/rotex0.html" target="_top">(<code class="filename">rotex0.php</code>)</a></code> </b></p><div class="figure-contents"> <span class="inlinemediaobject"><img src="images/rotex0.png" alt="Original unrotated graph (rotex0.php)"></span> </div></div><p><br class="figure-break">
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</p>
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<p>In <a class="xref" href="ch14s12.html#fig.rotex1" title="Figure 14.75. Rotating the plot area 45 degrees (rotex1.php)">Figure 14.75. Rotating the plot area 45 degrees <code class="uri"><a class="uri" href="example_src/rotex1.html" target="_top">(<code class="filename">rotex1.php</code>)</a></code> </a> and <a class="xref" href="ch14s12.html#fig.rotex2" title="Figure 14.76. Rotating the plot area 90 degrees (rotex2.php)">Figure 14.76. Rotating the plot area 90 degrees <code class="uri"><a class="uri" href="example_src/rotex2.html" target="_top">(<code class="filename">rotex2.php</code>)</a></code> </a> we
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have rotated the plot area around (the default) the center of the plot
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area</p>
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<p>
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</p><div class="informaltable">
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<table border="0"><colgroup><col class="c1"><col class="c2"></colgroup><tbody><tr><td>
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<p>
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</p><div class="figure"><a name="fig.rotex1"></a><p class="title"><b>Figure 14.75. Rotating the plot area 45 degrees <code class="uri"><a class="uri" href="example_src/rotex1.html" target="_top">(<code class="filename">rotex1.php</code>)</a></code> </b></p><div class="figure-contents"> <span class="inlinemediaobject"><img src="images/rotex1.png" alt="Rotating the plot area 45 degrees (rotex1.php)"></span> </div></div><p><br class="figure-break">
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</p>
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</td><td>
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<p>
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</p><div class="figure"><a name="fig.rotex2"></a><p class="title"><b>Figure 14.76. Rotating the plot area 90 degrees <code class="uri"><a class="uri" href="example_src/rotex2.html" target="_top">(<code class="filename">rotex2.php</code>)</a></code> </b></p><div class="figure-contents"> <span class="inlinemediaobject"><img src="images/rotex2.png" alt="Rotating the plot area 90 degrees (rotex2.php)"></span> </div></div><p><br class="figure-break">
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</p>
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</td></tr></tbody></table>
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</div><p>
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</p>
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<p>In the above two example the center of the rotation was the center point of
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the plot area. If we instead change the center of rotation to be the center of
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the entire graph we get the result shown in <a class="xref" href="ch14s12.html#fig.rotex3" title="Figure 14.77. Rotating the plot area 45 degrees (rotex3.php)">Figure 14.77. Rotating the plot area 45 degrees <code class="uri"><a class="uri" href="example_src/rotex3.html" target="_top">(<code class="filename">rotex3.php</code>)</a></code> </a> and
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<a class="xref" href="ch14s12.html#fig.rotex4" title="Figure 14.78. Rotating the plot area 90 degrees (rotex4.php)">Figure 14.78. Rotating the plot area 90 degrees <code class="uri"><a class="uri" href="example_src/rotex4.html" target="_top">(<code class="filename">rotex4.php</code>)</a></code> </a> . </p>
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<p>
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</p><div class="informaltable">
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<table border="0"><colgroup><col class="c1"><col class="c2"></colgroup><tbody><tr><td>
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<p>
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</p><div class="figure"><a name="fig.rotex3"></a><p class="title"><b>Figure 14.77. Rotating the plot area 45 degrees <code class="uri"><a class="uri" href="example_src/rotex3.html" target="_top">(<code class="filename">rotex3.php</code>)</a></code> </b></p><div class="figure-contents"> <span class="inlinemediaobject"><img src="images/rotex3.png" alt="Rotating the plot area 45 degrees (rotex3.php)"></span> </div></div><p><br class="figure-break">
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</p>
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</td><td>
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<p>
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</p><div class="figure"><a name="fig.rotex4"></a><p class="title"><b>Figure 14.78. Rotating the plot area 90 degrees <code class="uri"><a class="uri" href="example_src/rotex4.html" target="_top">(<code class="filename">rotex4.php</code>)</a></code> </b></p><div class="figure-contents"> <span class="inlinemediaobject"><img src="images/rotex4.png" alt="Rotating the plot area 90 degrees (rotex4.php)"></span> </div></div><p><br class="figure-break">
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</p>
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</td></tr></tbody></table>
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</div><p>
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</p>
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<p>As a final example in <a class="xref" href="ch14s12.html#fig.rotex5" title="Figure 14.79. Rotating the plot area -30 degree around the bottom left corner (rotex5.php)">Figure 14.79. Rotating the plot area -30 degree around the bottom left corner <code class="uri"><a class="uri" href="example_src/rotex5.html" target="_top">(<code class="filename">rotex5.php</code>)</a></code> </a> we show the result of
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rotating the plot area -30 degree around the bottom left point in the
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graph</p>
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<p>
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</p><div class="figure"><a name="fig.rotex5"></a><p class="title"><b>Figure 14.79. Rotating the plot area -30 degree around the bottom left corner <code class="uri"><a class="uri" href="example_src/rotex5.html" target="_top">(<code class="filename">rotex5.php</code>)</a></code> </b></p><div class="figure-contents"> <span class="inlinemediaobject"><img src="images/rotex5.png" alt="Rotating the plot area -30 degree around the bottom left corner (rotex5.php)"></span> </div></div><p><br class="figure-break">
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</p>
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</div>
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<div class="sect2" title="Rotating the plot area 90 degree"><div class="titlepage"><div><div><h3 class="title"><a name="id2551820"></a>Rotating the plot area 90 degree</h3></div></div></div>
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<p>As can be seen above in <a class="xref" href="ch14s12.html#fig.rotex2" title="Figure 14.76. Rotating the plot area 90 degrees (rotex2.php)">Figure 14.76. Rotating the plot area 90 degrees <code class="uri"><a class="uri" href="example_src/rotex2.html" target="_top">(<code class="filename">rotex2.php</code>)</a></code> </a> and <a class="xref" href="ch14s12.html#fig.rotex4" title="Figure 14.78. Rotating the plot area 90 degrees (rotex4.php)">Figure 14.78. Rotating the plot area 90 degrees <code class="uri"><a class="uri" href="example_src/rotex4.html" target="_top">(<code class="filename">rotex4.php</code>)</a></code> </a> the rotation does not alter the overall size and
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margin of the graph even though we probably should do so in order to better
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accommodate the rotated plot areas topography. It is of course perfectly
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possible to adjust the size of the graph manually.</p>
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<p>The slight complication with general rotation is that the margins also
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rotates, this means that if the graph is rotated 90 degrees the left margin in
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the image was originally the bottom margin. In additional by default the center
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of the rotation is the center of the plot area and not the entire image (if all
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the margins are symmetrical then they will of course coincide). This means the
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center of the rotation will move with the margin (since the specify the exact
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location of the plot area)..</p>
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<p>So for the case of rotating a graph 90 degree the library provides a
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convenience method to do both the rotation and specifying the margin at the same
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time (to avoid the mental exercise described above) by providing the
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method</p>
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<p>
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</p><div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
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<p><code class="code">Set90AndMargin(($aLeft=0,$aRight=0,$aTop=0,$aBottom=0)
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</code></p>
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<p>Rotates the plot area 90 degrees and sets the graph margin
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areas</p>
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</li></ul></div><p>
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</p>
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<p>This method is probably most commonly used with bar graphs to create
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horizontal instead of vertical bars. See the section on bar graphs, ??, for more
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example on this.</p>
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</div>
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</div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"> </td><td width="20%" align="center"><a accesskey="u" href="ch14.html">Up</a></td><td width="40%" align="right"> </td></tr><tr><td width="40%" align="left" valign="top"> </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> </td></tr></table></div></body></html>
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