rollstat( y, window, slide,funin)

Unlike most rolling-window tools, rollstat accepts a time-series (or other sequence) of samples which are not necessarily equally spaced -- in fact multiple samples at a given x-value are allowed. The "window" and "slide" arguments are used to group the samples by the true time/distance window regardless of how many samples end up assigned to a given window. There's a default statistic function or the user can supply his own function.