convTime2PhysicalIndex

  convTime2PhysicalIndex converts time to linear indices into a waveform
  matrix

  Example:
  idx=convTime2PhysicalIndex(channel, time)
  idx=convTime2PhysicalIndex(channel, start, stop)
        channel is a sigTOOL channel array cell element
        time or start & stop are the times to convert

  idx contains the start and stop indices in columns 1 and 2 respectively

  When a single time is specified, idx is the index into adc for the sample
  at the specified time or the first sample afterwards
  When start and stop are given, idx are indices into the adc field such 
  that sampling occurred between the limits
                            start <= t < stop.

  With episodic or framed waveforms, idx will be a matrix of indices with
  one row for each period contained in the interval start to stop.
  e.g.
                idx=convTime2PhysicalIndex(channels{1}, 0, 500000);
  might return
                  idx =
                             1       16001
                         16002       32002
                         32003       48003
                         48004       64004
                         64005       80005
  Access the first period with:
                      data=channels{1}.adc(idx(1,1):idx(1,2));


  convTime2PhysicalIndex differs from findVectorIndices in that the returned
  indices are linear indices into the adc matrix, not indices into the
  column vector representing a specific epoch

  See also ind2sub, sub2ind

 -------------------------------------------------------------------------
  Author: Malcolm Lidierth 09/06
  Copyright © The Author & King’s College London 2006-2007
 -------------------------------------------------------------------------

  Acknowledgements:
  Revisions: