transformation of a date into a higher frequency date
datnew=datelf2hf(dat,divfq,ind)
dat = a string representing a grocer date
fq = the destination frequency
ind = a scalar equal to the high frequency part of the initial date
daten = the corresponding high frequency date
datelf2hf('1989q1',3,1) // gives '1989m1' datelf2hf('1989a',4,2) // gives '1989q2'.