LOG   Base 2 logarithm of data matrix

     B=LOG2(A)

 INPUT
    A   SDDATA object

 OUTPUT
    B   SDDATA object

 DESCRIPTION
 LOG computes base 2 logarithm of data set A. Error is raised if the
 output becomes complex. This assures SDDATA object contains always double
 data type.

 SEE ALSO
 LOG, LOG10