Parent Topic: <A href="http://www.pcigeomatics.com/cgi-bin/pcihlp/IWORKS">IWORKS</a><hr>
<H3>Session Scatter Plot</H3>
A scatterplot is a combination of the histograms of two channels
showing the correlation between these histograms.  The graph represents
a 256x256 matrix with the bottom leftmost pixel representing the number
of pixels that are zero at the same location in each image.  Similarly,
the bottom right pixel represents the number of pixels that have the
value of 255 in the X-Axis channel and 0 in the Y-axis channel at the
same location in each image.<p>
The values in the 256x256 matrix are encoded such that higher values
appear brighter in grey scale mode, or warmer in pseudocolour mode. 
For channels which are not 8-bit, the channels are scaled to a 0 to 255
range first, before computing the scatterplot.<p>
You may selectively view certain parts of the scatterplot by zooming.
This may be accomplished in one of two ways.  First, you may click and
drag out a rectangle indicating your desired region of interest.  The
``Show All'' button will allow you to see the entire graph again.  Second,
you may use the Ctrl-Left Mouse button or Ctrl-Right Mouse button to zoom
in and out respectively.
<P>
<H4>Colour</H4>
There are two allowable colouring schemes used for coding the frequency
values used in the scatter plot: a grey scale, and a pseudocolour scale. 
These options are displayed as the &quot;Colour&quot; radio buttons on the scatter
plot panel.  The grey scale uses 256 shades of grey to code frequency
values, black being the least frequent and white being the most frequent.
The pseudocolour scale uses a pseudocolour table to code frequency values,
with black, again, representing the least frequent value, and red
representing the most frequent.  Users can toggle between the two colour 
schemes if they wish, simply by selecting the appropriate radio button.
<P>
<H4>Sample </H4>
The user can toggle between using the entire file as data for the scatter
plot, or using selected classes as masks to limit the amount of data that
actually goes into the scatter plot.  The selected classes are the
highlighted ones in the class table.  If no class is selected, the scatter
plot is a blank graph.
<P>
<H4>Hide Controls/ShowControls</H4>
The Hide Controls button will resize the panel so that the scatter plot
fills the entire window.  The control and statistics areas will not be
visible.  After the button is pressed, its title will change to
&quot;Show Controls&quot;.  Pressing this button again will restore the panel to
its original shape.<p>
The Hide Controls Button is useful if the user has already done all that
needs to be done in the way of configuring the scatter plot, and just
wishes to examine the actual graph.  It is also useful for comparing
two scatter plots on separate panels, as control areas, in this instance,
often distract the user from the task at hand.
<P>
<H4>Class Table</H4>
The Class Table allows the user to control how much data is visible on the
scatter plot at any one time.  <p>
Plot Mean - clicking this cell for a particular class will toggle the
visibility of that class' mean value on the scatter plot.  One can have
as many or as little mean values visible as needed.<p>
Plot Ellipse - clicking this cell for a particular class will toggle the
visibility of that class' associated ellipse on the scatter plot.  One can
have as many or as few ellipses visible as needed.<p>
The remaining cells simply display data relevant to the classes. 
These are not editable.
<P>
<hr>
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