trend2d - Fit a [weighted] [robust] polynomial model for z = f(x,y) to xyz[w] data. trend2d -F < xyzmrw > -N n _ model [ r ] [ xyz [ w ] file ] [ -C condition _# ] [ -H [ nrec ] ][ -I [ confidence _ level ] ] [ -V ] [ -W ] [ -: ] [ -bi [ s ][ n ] ] [ -bo [ s ] ] trend2d reads x,y,z [and w] values from the first three [four] columns on standard input [or xyz [ w ] file ] and fits a regression model z = f(x,y) + e by [weighted] least squares. ... Optionally, append r to perform a robust fit. ...