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  28  <H2><A NAME="8_3">8.3 Error plots</A></H2>
  29  <P> Error plots are used to visually indicate uncertainty in data
  30   points. This is done by for each X value by giving both a minimum and a
  31   maximum Y-value.</P>
  32  <P> Before you can use error plots you must remember to include the file
  33   &quot;jpgraph_error.php&quot; in your script.</P>
  34  <P> The following example illustrates a simple error bar. We will have 5
  35   points, so we need 10 Y-values. We also would like the error bars to be
  36   red and 2 pixels wide. All this is accomplished by creating an <A href="../ref/ErrorPlot.html#_C_ERRORPLOT">
  37   ErrorPlot()</A> in much the same way as, for example, a normal line
  38   plot. Doing this would now give the example shown below.</P>
  39  <P><DIV class="example">
  40  <BR> <A href="exframes/frame_example13.html" target="blank"><IMG border="0"
  41  HEIGHT="200"  src="img/example13.png" WIDTH="300"></A>
  42  <BR><B>Figure 53:</B> A simple error bar <A href="exframes/frame_example13.html"
  43  target="blank">[src]</A>&nbsp;
  44  <P></P>
  45  </DIV></P>
  46  <P> You might notice that there is one displeasing esthetic quality of
  47   this graph. The X-scale is just wide enough to just accompany the
  48   number of error bars and hence the first bar is drawn on the Y-axis and
  49   the and last bar just at the edge of the plot area. To adjust this you
  50   might call the <A href="../ref/Plot.html#_PLOT_SETCENTER"> SetCenter()</A>
  51   method which will adjust the X-scale so it does not use the full width
  52   of the X-axis.</P>
  53  <P> The following example illustrates the use of this feature by
  54   applying this technique to the previous example<DIV class="example">
  55  <BR> <A href="exframes/frame_example14.html" target="blank"><IMG border="0"
  56  HEIGHT="200"  src="img/example14.png" WIDTH="300"></A>
  57  <BR><B>Figure 54:</B> Adjusting the X-scale not to use the full width of
  58   the X-axis. <A href="exframes/frame_example14.html" target="blank">
  59  [src]</A>&nbsp;
  60  <P></P>
  61  </DIV></P>
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