[Sommaire] [Imprimer]

   1  <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
   2  <HTML>
   3  <HEAD>
   4  <META HTTP-EQUIV="Content-Type" CONTENT="text/html; CHARSET=iso-iso-8859-1">
   5  <LINK REL="Start" HREF="index.html">
   6  <LINK REL="Contents" HREF="toc.html">
   7  <LINK REL="Prev" HREF="8195InvertingtheYaxis.html">
   8  <LINK REL="Next" HREF="821Addingbandsofpatternandcolortographs.html">
   9  <STYLE TYPE="text/css"><!--
  10  BODY { font-family: serif }
  11  H1 { font-family: sans-serif }
  12  H2 { font-family: sans-serif }
  13  H3 { font-family: sans-serif }
  14  H4 { font-family: sans-serif }
  15  H5 { font-family: sans-serif }
  16  H6 { font-family: sans-serif }
  17  SUB { font-size: smaller }
  18  SUP { font-size: smaller }
  19  PRE { font-family: monospace }
  20  A { text-decoration: none }
  21  --></STYLE>
  22  </HEAD>
  23  <BODY>
  24  <A HREF="toc.html">Contents</A>
  25  <A HREF="8195InvertingtheYaxis.html">Previous</A>
  26  <A HREF="821Addingbandsofpatternandcolortographs.html">Next</A>
  27  <HR NOSHADE>
  28  <H2><A NAME="8_20">8.20 Adjusting the auto-scaling limits - grace value</A>
  29  </H2>
  30  <P> By default the auto-scaling algorithm tries to make best possible
  31   use of screen estate by making the scale as large as possible, i.e. the
  32   extreme values (min/max) will be on the top and bottom of the scale if
  33   they happen to fall on a scale-tick. So for example doing a simple line
  34   plot could look like the plot shown in the below.<DIV class="example">
  35  <BR> <A href="exframes/frame_example3.2.html" target="blank"><IMG border="0"
  36  HEIGHT="200"  src="img/example3.2.png" WIDTH="300"></A>
  37  <BR><B>Figure 96:</B> A typical graph with autoscaling and grace=0 <A href="exframes/frame_example3.2.html"
  38  target="blank">[src]</A>&nbsp;
  39  <P></P>
  40  </DIV></P>
  41  <P> However you might sometime want to add some extra to the minimum and
  42   maximum values so that there is some &quot;air&quot; in the graph between the end
  43   of the scale values and the extreme points in the graphs. This can be
  44   done by adding a &quot;grace&quot; percentage to the scale. So for example adding
  45   10% to the y-scale in the image above is done by calling the <A href="../ref/LinearScale.html#_LINEARSCALE_SETGRACE">
  46   SetGrace()</A> method on the yscale as in</P>
  47  <P><DIV class="phpscript"><CODE><FONT color="#000000"> <FONT color="#0000BB">
  48  &nbsp;$graph</FONT><FONT color="#007700">-&gt;</FONT><FONT color="#0000BB">yaxis</FONT><FONT
  49  color="#007700">-&gt;</FONT><FONT color="#0000BB">scale</FONT><FONT color="#007700">
  50  -&gt;</FONT><FONT color="#0000BB">SetGrace</FONT><FONT color="#007700">(</FONT><FONT
  51  color="#0000BB">10</FONT><FONT color="#007700">,</FONT><FONT color="#0000BB">
  52  10</FONT><FONT color="#007700">);</FONT><FONT color="#0000BB"></FONT></FONT>
  53  </CODE></DIV></P>
  54  <P> These lines add a minimum of 10% to the top and bottom values of the
  55   scale. Note that we say &quot;minimum&quot; since depending on the specific tick
  56   values choose this might be a little bit more to make the end of the
  57   scale fall on an even tick mark.</P>
  58  <P> Adding this line to the previous graph will result in the following
  59   example</P>
  60  <P><DIV class="example">
  61  <BR> <A href="exframes/frame_example3.2.1.html" target="blank"><IMG border="0"
  62  HEIGHT="200"  src="img/example3.2.1.png" WIDTH="300"></A>
  63  <BR><B>Figure 97:</B> Adding 10% grace value to top and bottom of the
  64   Y-scale <A href="exframes/frame_example3.2.1.html" target="blank">[src]</A>
  65  &nbsp;
  66  <P></P>
  67  </DIV></P>
  68  <P> Since we haven't adjusted the position of the X-axis it will remain
  69   at Y=0 which might not necessary be what we would like so we therefor
  70   also add the line</P>
  71  <P><DIV class="phpscript"><CODE><FONT color="#000000"> <FONT color="#0000BB">
  72  &nbsp;$graph</FONT><FONT color="#007700">-&gt;</FONT><FONT color="#0000BB">xaxis</FONT><FONT
  73  color="#007700">-&gt;</FONT><FONT color="#0000BB">SetPos</FONT><FONT color="#007700">
  74  (</FONT><FONT color="#DD0000">&quot;min&quot;</FONT><FONT color="#007700">);</FONT><FONT
  75  color="#0000BB"></FONT></FONT></CODE></DIV></P>
  76  <P></P>
  77  <P> So that the X-axis always will remain at the lowest possible
  78   Y-value. Doing this will then result in the example below</P>
  79  <P><DIV class="example">
  80  <BR> <A href="exframes/frame_example3.2.2.html" target="blank"><IMG border="0"
  81  HEIGHT="200"  src="img/example3.2.2.png" WIDTH="300"></A>
  82  <BR><B>Figure 98:</B> Using grace but also adjusting the position of the
  83   X-axis <A href="exframes/frame_example3.2.2.html" target="blank">[src]</A>
  84  &nbsp;
  85  <P></P>
  86  </DIV></P>
  87  <P></P>
  88  <HR NOSHADE>
  89  <A HREF="toc.html">Contents</A>
  90  <A HREF="8195InvertingtheYaxis.html">Previous</A>
  91  <A HREF="821Addingbandsofpatternandcolortographs.html">Next</A>
  92  </BODY>
  93  </HTML>