plots forecasts of difference with confidence bars
ec.gfd(obj, whichseries = 1, nsigma = 3, xvec, yvec, cal, lar = 0.025, ...)output of ec.main
series number
how many standard deviations in confidence bars
vector of dates to place on x axis
vector of exp(y) values to display on y axis
calendar vector
length of arrows in error bars
other plot parameters
does not return output, just creates a graph