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  28  <H3><A NAME="8_1_5">8.1.5 Adding a legend to the graph</A></H3>
  29  <P> With more than one plot on the same graph it is necessary to somehow
  30   indicate which plot is which. This is normally done by adding a legend
  31   to the graph.</P>
  32  <P> You will see that each plot type has a 'SetLegend()' method which is
  33   used to name that plot in the legend. SO to name the two plots in the
  34   example we have been working with so far we need to add the lines<DIV class="phpscript">
  35  <CODE><FONT color="#000000"> <FONT color="#0000BB">&nbsp;$lineplot</FONT><FONT
  36  color="#007700">-&gt;</FONT><FONT color="#0000BB">SetLegend</FONT><FONT color="#007700">
  37  (</FONT><FONT color="#DD0000">&quot;Plot&nbsp;1&quot;</FONT><FONT color="#007700">);
  38  <BR></FONT><FONT color="#0000BB">$lineplot2</FONT><FONT color="#007700">
  39  -&gt;</FONT><FONT color="#0000BB">SetLegend</FONT><FONT color="#007700">(</FONT><FONT
  40  color="#DD0000">&quot;Plot&nbsp;2&quot;</FONT><FONT color="#007700">);</FONT><FONT color="#0000BB">
  41  </FONT></FONT></CODE></DIV></P>
  42  <P> to the previous code. The resulting graph is shown below
  43  <!--?
  44  Example('example5.1','Adding a legend to the graph');
  45  ?-->
  46   As you can see the legend gets automatically sized depending on how
  47   many plots there are that have legend texts to display. By default it
  48   is placed with it's top right corner close to the upper right edge of
  49   the image. Depending on the image you might want to adjust this or you
  50   might want to add a larger margin which is big enough to accompany the
  51   legend. Let's do both.</P>
  52  <P> First we increase the right margin and then we place the legend so
  53   that it is roughly centered. We will also enlarge the overall image so
  54   the plot area doesn't get too squeezed.</P>
  55  <P> To modify the legend you access the 'legend' property of the graph.
  56   For a full reference on all the possibilities (changing colors, layout,
  57   etc) see <A href="../ref/Legend.html#_C_LEGEND/">class legend</A> in
  58   the class reference</P>
  59  <P> For this we use the legends 'SetPos()' method as in<DIV class="phpscript">
  60  <CODE><FONT color="#000000"> <FONT color="#0000BB">&nbsp;$graph</FONT><FONT color="#007700">
  61  -&gt;</FONT><FONT color="#0000BB">legend</FONT><FONT color="#007700">-&gt;</FONT><FONT
  62  color="#0000BB">Pos</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">
  63  0.05</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">0.5</FONT><FONT
  64  color="#007700">,</FONT><FONT color="#DD0000">&quot;right&quot;</FONT><FONT color="#007700">
  65  ,</FONT><FONT color="#DD0000">&quot;center&quot;</FONT><FONT color="#007700">);</FONT><FONT
  66  color="#0000BB"></FONT></FONT></CODE></DIV></P>
  67  <P></P>
  68  <P> Doing this small modification will give the result shown below<DIV class="example">
  69  <BR> <A href="exframes/frame_example6.html" target="blank"><IMG border="0"
  70  HEIGHT="200"  src="img/example6.png" WIDTH="400"></A>
  71  <BR><B>Figure 11:</B> Adjusting the layout to give more rooms for the
  72   legend <A href="exframes/frame_example6.html" target="blank">[src]</A>&nbsp;
  73  <P></P>
  74  </DIV></P>
  75  <P> The above method 'SetPos()' deserves some explanation since it might
  76   not be obvious. You specify the position as a fraction of the overall
  77   width and height of the entire image. This makes it possible for you to
  78   resize the image within disturbing the relative position of the legend.
  79   We will later see that the same method is just to place arbitrary text
  80   in the image.</P>
  81  <P> To give added flexibility one must also specify to what edge of the
  82   legend the position given should be relative to. In the example above
  83   we have specified &quot;right&quot; edge on the legend for the for the horizontal
  84   positioning and &quot;center&quot; for the vertical position.</P>
  85  <P> This means that the right edge of the legend should be position 5 %
  86   of the image width from the right. If you had specified &quot;left&quot; the the
  87   legends left edge would be positioned 5 % of the image width from the
  88   image left side.</P>
  89  <P> By default the legends in the legend box gets stacked on top of each
  90   other. The other possibility is to have them sideways. To adjust this
  91   you use the <A href="../ref/Legend.html#_LEGEND_SETLAYOUT">SetLayout()</A>
  92   method. Using a horizontal layout with the previous example give the
  93   following result.<DIV class="example">
  94  <BR> <A href="exframes/frame_example6.1.html" target="blank"><IMG border="0"
  95  HEIGHT="240"  src="img/example6.1.png" WIDTH="300"></A>
  96  <BR><B>Figure 12:</B> Using a horizontal layout for the legends <A href="exframes/frame_example6.1.html"
  97  target="blank">[src]</A>&nbsp;
  98  <P></P>
  99  </DIV></P>
 100  <P></P>
 101  <H4>8.1.5.1 Adjusting the layout of the legend</H4>
 102  <P> For more advanced fomatting of the legend it is possible to adjust</P>
 103  <UL>
 104  <LI> The number of columns in the legend</LI>
 105  <LI> Specify vertical / horizontal margins for legend columns</LI>
 106  </UL>
 107  <P> In order to adjust the number of columns used in the legend the
 108   method<I> Legend::SetColumns</I> is used. So for example to have the
 109   legend lined up using three columns the follwing lines have to be added
 110   to teh script<DIV class="phpscript"><CODE><FONT color="#000000"> <FONT color="#0000BB">
 111  &nbsp;$graph</FONT><FONT color="#007700">-&gt;</FONT><FONT color="#0000BB">
 112  legend</FONT><FONT color="#007700">-&gt;</FONT><FONT color="#0000BB">
 113  SetColumns</FONT><FONT color="#007700">(</FONT><FONT color="#0000BB">3</FONT><FONT
 114  color="#007700">);</FONT><FONT color="#0000BB"></FONT></FONT></CODE></DIV>
 115  </P>
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