date2num_fq — transforms a date into a number and its frequency
[num,fq]=date2num_fq(dat)
dat = a date string
indw = 'w' if the date is given as a day date but corresponds to a week (optional)
num = the numerical representation of the dates
fq = its frequency
[num,fq]=date2num_fq('1985q4') // return the numerical representation and frequency of the quarterly date '1985q4' num,fq]= date2num_fq ('2002a') // return the numerical representation and frequency of the yearly date '2002a'. [num,fq]= date2num_fq ('97m12') // return the numerical representation and frequency of the monthly date '97m12'. [num,fq]= date2num_fq ('2002/03/15','w') // return the numerical representation and frequency of the daily date '2000/03/15'.