expand a original series into a monthly one
tsout=b2m(tsin)
* tsin = a time series available every two months
* option = an integer, between -1 and 2:
. -1 if each monthly value is equal to the original one (default if the argument is not given)
. 0 if each monthly value is equal to the original one divided by 2
. n if the value of the n-th month is equal to the original one and the others are set to %nan
* tsout = the corresponding monthly time series
x = reshape([1:35],'1978b1') // create a ts avalaible every two months y = b2m(x) // gives a monthly ts, from 1978m1 to 1983m10 with values 1 for the first 2 months of 1978, // 2 for the 2 following months of 1978... y = b2m(x,2) // gives a monthly ts, from 1978m1 to 1983m10 with values %nan,1,%nan,2,... |  |  |