RestoreDiscClass

  RestoreDiscClass changes the class of the data in a MAT file (v6)

  Example:
  filename=RestoreDiscClass(FILENAME, VARNAME)

  FILENAME: The target file. Must be a v6 MAT-file
  VARNAME: string with the variable name

  VARNAME must be a standard matrix (numeric (including complex), logical
  or char) but may not be sparse. RestoreDiscClass works with both real and
  complex variables

  The MATLAB builin SAVE command casts data to the smallest class possible
  without causing loss of data. LOAD then casts back to the original class.
  RestoreDiscClass casts the data on disc to the original class. The target
  variable must be the final variable in the MAT-file i.e. it must be at
  the end of the file

  RestoreDiscClass should be called before using any of the AppendXXXXX
  functions to ensure that adequate bytes have been set aside to store
  the appended data without loss.

  FILENAME is returned by RestoreDiscClass prefixed with full path details.
  This can be used to avoid confusion if multiple files with the same name
  occur and no path is specified expicitly (although this would normally
  only cause problems if there are MAT files in the \private folder of the 
  MAT-utilities)
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  This program is distributed without any warranty,
  without even the implied warranty of fitness for a particular purpose.
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  Author: Malcolm Lidierth 11/06
  Copyright © The Author & King's College London 2006
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  Revisions:    04.11.07   Reposition code for no change: now faster