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<A HREF="toc.html">Contents</A>
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<A HREF="8210Creatingsemifilledbargraphs.html">Previous</A>
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<A HREF="831Usinglineerrorplots.html">Next</A>
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<HR NOSHADE>
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<H2><A NAME="8_3">8.3 Error plots</A></H2>
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<P> Error plots are used to visually indicate uncertainty in data
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points. This is done by for each X value by giving both a minimum and a
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maximum Y-value.</P>
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<P> Before you can use error plots you must remember to include the file
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"jpgraph_error.php" in your script.</P>
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<P> The following example illustrates a simple error bar. We will have 5
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points, so we need 10 Y-values. We also would like the error bars to be
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red and 2 pixels wide. All this is accomplished by creating an <A href="../ref/ErrorPlot.html#_C_ERRORPLOT">
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ErrorPlot()</A> in much the same way as, for example, a normal line
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plot. Doing this would now give the example shown below.</P>
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<P><DIV class="example">
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<BR> <A href="exframes/frame_example13.html" target="blank"><IMG border="0"
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HEIGHT="200" src="img/example13.png" WIDTH="300"></A>
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<BR><B>Figure 53:</B> A simple error bar <A href="exframes/frame_example13.html"
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target="blank">[src]</A>
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<P></P>
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</DIV></P>
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<P> You might notice that there is one displeasing esthetic quality of
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this graph. The X-scale is just wide enough to just accompany the
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number of error bars and hence the first bar is drawn on the Y-axis and
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the and last bar just at the edge of the plot area. To adjust this you
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might call the <A href="../ref/Plot.html#_PLOT_SETCENTER"> SetCenter()</A>
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method which will adjust the X-scale so it does not use the full width
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of the X-axis.</P>
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<P> The following example illustrates the use of this feature by
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applying this technique to the previous example<DIV class="example">
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<BR> <A href="exframes/frame_example14.html" target="blank"><IMG border="0"
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HEIGHT="200" src="img/example14.png" WIDTH="300"></A>
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<BR><B>Figure 54:</B> Adjusting the X-scale not to use the full width of
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the X-axis. <A href="exframes/frame_example14.html" target="blank">
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[src]</A>
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<P></P>
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