Calculate the moving sum. For compatibility only.
mov.sum(x, k, shift = "centre")A vector to calculate moving sum
The moving windows
if shift = "centre", then values are shifted to centre. if shift = "begin", then values are at begin of period. if shift = "end", then values are at end of period. The default value (centre) will be used if shift is other value.
The moving sum of vector x at moving windows k