15.64.49.15  USER       - 
     USER=n1,n1...  specifies the type of user scale.  This is only useful
if you supply your own scaling routines.  n1 is the scale type.   n2...n10
are values passed to the user routine.  The user function is called:
     Value=TDFNCT(X,SCALE)
X is the value to rescale.
SCALE(10) is the array of values n1...n10.
For example a log scale would be:  TDFNCT=ALOG(X)