seasdummy — create a seasonal dummy variable
dum=seasdummy(boun,subperiod)
boun = a (2x1) string vector of dates
subperiod = a scalar corresponding the yearly period when the dummy variables is set to 1 (for instance 3 for a march-june-september-december dummy with monthly data)
dummy = a ts equal to 1 for the chosen season, O otherwise
m3=seasdummy(['1970m1';'2007m3'],3) // creates a seasonal dummy variable on the period going // from the 1st month of 1970 until the the 3rd month of 2007, equal to 1 every third month // of the year (on march therefore!) and 0 elsewhere. q1=seasdummy(['1970q1';'2007q4'],1) // creates a seasonal dummy variable on the period going // from the 1st quarter of 1970 until the the last quarter of 2007, equal to 1 every first quarter and 0 elsewhere