[Sommaire] [Imprimer]

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  27  <HR NOSHADE>
  28  <H2><A NAME="8_4">8.4 Scatter plots</A></H2>
  29  <P> Scatter plots are very simple; they plot a number of points
  30   specified by their X- and Y-coordinate. Each point is stroked on the
  31   image with a mark as with line plots. The stroked marks can also be
  32   connected with an optional line.<DIV class="note"><B>Note:</B> Even
  33   though it is only scatter plot that was designed to be used with X,Y
  34   plots it is perfectly possible to use use both X,Y coordinates for bar
  35   and line plots as well.</DIV></P>
  36  <P> Even though you would normally supply X-coordinates it is still
  37   perfectly possible to use a text-scale for X-coordinates to just
  38   enumerate the points. This is especially useful when using the
  39   &quot;Impulse&quot; type of scatter plot as is shown below.</P>
  40  <P> Scatter pots are created by including the jpgraph extension
  41   &quot;jpgraph_scatter.php&quot; and then creating an instance of plot type of
  42   ScatterPlot(). To specify the mark you want to use you access the mark
  43   with the instance variable &quot;mark&quot; in the scatter plot. The default is
  44   to use an unfilled small circle.</P>
  45  <P> To create a scatter plot you will create an instance</P>
  46  <P> A simple example using just default values will illustrate this</P>
  47  <P><DIV class="example">
  48  <BR> <A href="exframes/frame_scatterex1.html" target="blank"><IMG border="0"
  49  HEIGHT="200"  src="img/scatterex1.png" WIDTH="300"></A>
  50  <BR><B>Figure 57:</B> The simplest possible scatter plot <A href="exframes/frame_scatterex1.html"
  51  target="blank">[src]</A>&nbsp;
  52  <P></P>
  53  </DIV></P>
  54  <P>We can easily adjust the size and colors for the markers to get
  55   another effect as shown below<DIV class="example">
  56  <BR> <A href="exframes/frame_scatterex2.html" target="blank"><IMG border="0"
  57  HEIGHT="200"  src="img/scatterex2.png" WIDTH="300"></A>
  58  <BR><B>Figure 58:</B> The simplest possible scatter plot with adjusted
  59   marks <A href="exframes/frame_scatterex2.html" target="blank">[src]</A>
  60  &nbsp;
  61  <P></P>
  62  </DIV></P>
  63  <P> Another possible variant of scatter plot is impulse-scatter plots.
  64   This is a variant of normal scatter plot where each mark have a line
  65   from the mark to the Y=0 base line. To change a scatter plot into an
  66   impulse scatter plot you have to call the method <A href="../ref/ScatterPlot.html#_SCATTERPLOT_SETIMPULS">
  67   SetImpuls()</A> on the scatter plot.</P>
  68  <P> This type of plots are often used to illustrate signals in
  69   conjunction with digital signal processing. The following two examples
  70   illustrates simple use of impulse plots.<DIV class="example">
  71  <BR> <A href="exframes/frame_impulsex1.html" target="blank"><IMG border="0"
  72  HEIGHT="200"  src="img/impulsex1.png" WIDTH="300"></A>
  73  <BR><B>Figure 59:</B> A simple impuls plot <A href="exframes/frame_impulsex1.html"
  74  target="blank">[src]</A>&nbsp;
  75  <P></P>
  76  </DIV></P>
  77  <P> The next example shows how to modify the color and width of the
  78   impulse plot<DIV class="example">
  79  <BR> <A href="exframes/frame_impulsex2.html" target="blank"><IMG border="0"
  80  HEIGHT="200"  src="img/impulsex2.png" WIDTH="300"></A>
  81  <BR><B>Figure 60:</B> A modified impuls plot <A href="exframes/frame_impulsex2.html"
  82  target="blank">[src]</A>&nbsp;
  83  <P></P>
  84  </DIV></P>
  85  <P><DIV class="note"><B>Note:</B> You may draw impulse graphs without
  86   any mark by specifying the mark type as (-1) . That way only the
  87   impulse lines will be drawn.</DIV></P>
  88  <P> As a final touch we show two more advanced impulse graphs . In these
  89   graphs we have used more advanced formatting for the Y-axis labels as
  90   well as adjusted the position of the axis position.<DIV class="example">
  91  <BR> <A href="exframes/frame_impulsex3.html" target="blank"><IMG border="0"
  92  HEIGHT="200"  src="img/impulsex3.png" WIDTH="400"></A>
  93  <BR><B>Figure 61:</B> In this imuplsplot we have adjusted the position
  94   of the X-axis to the bottom and also added more decimals to the labels
  95   on the Y-axis <A href="exframes/frame_impulsex3.html" target="blank">
  96  [src]</A>&nbsp;
  97  <P></P>
  98  </DIV></P>
  99  <P><DIV class="example">
 100  <BR> <A href="exframes/frame_impulsex4.html" target="blank"><IMG border="0"
 101  HEIGHT="250"  src="img/impulsex4.png" WIDTH="500"></A>
 102  <BR><B>Figure 62:</B> In this impuls plot we have also added a lineplot
 103   with a dotted line style. <A href="exframes/frame_impulsex4.html" target="blank">
 104  [src]</A>&nbsp;
 105  <P></P>
 106  </DIV></P>
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