Documentation describing how to extract eignvectors added to pca. Fixes #2166

  <description>

      This programs converts a cube into principal component space or

        converts a cube back from principal component space.

        reverses a cube from principal component space. The principal component analysis (PCA) is performed over all bands of the input cube. The <b>n x n</b> transformation matrix used for this conversion is attached to the output cube as a table, where <b>n</b> is the number of bands of the input cube. Each vertical column in the transformation matrix is an eigenvector. 

     <br /> <br /> 

    To run the program, you must provide an input cube, specify an output cube name, and select either Transform or Inverse as your transformation mode of choice

    <br /><br />

     The transformation matrix can be extracted by using the following command:

    <p>

     <blockquote>

        tabledump from=[cube name].cub name="Transform Matrix"

     </blockquote>

    </p>

  </description>

  <category>

    <change name="Steven Lambright" date="2008-05-13">

      Removed references to CubeInfo 

    </change>

    <change name="Kristin Berry" date="2014-09-18">

      Improved documentation      

    </change>

  </history>

  <groups>