Correlation Pursuit

Selecting this button generates a window in which a projection pursuit
index for the current two dimensional view of the data is plotted.  As
the correlation tour progresses the index is plotted continuously.
The value is also displayed directly beneath this button.

Selecting this button also turns on the "Sphere" button and spheres
the data by sphering each of the two sets of variables. For the one
index currently available sphering is not necessary.

When "Optimz" is selected, the correlation tour is guided by the
gradient of the coreelation pursuit index, so that XGobi begins to
search for views with high index values.  Hopefully these views will
expose interesting features of the data.  When a maximum value of the
index is reached the tour may turn itself off (this occurs when the
gradients are all close to zero, meaning we have gone as far as
possible in this direction to capture a maximum, and it is not
possible to find any better direction).  To restart the correlation
tour turn "Optimz" off.

The only index currently available is the correlation between the two
projections (horizontal and vertical) displayed.