mergeSeries(x, y, differences = F)tis objects, or objects that can sensibly be coerced to
tis by as.tis.T, the first differences of series are merged, and then
cumulatively summed. The default is F.tis object series with start and end dates that span those of
x and y. Where the series overlap, values from y
are used.x and y must have the same tif (ti frequency),
and the same number of column (if they are multivariate).cbind.tis