I have a very large file with many rows and columns. I want to create a plot with lowess. If I try the following it works fine: data(PrecipGL) plot(PrecipGL) lines(lowess(time(PrecipGL),PrecipGL),lwd=3, col=2) In my file, 2 columns are "nox" and "sdate", and are both typeof() = double. If I issue command Plot(nox~sdate) I can get a nice plot. However if I try lines(lowess(time(nox~sdate),nox~sdate),lwd=3, col=2) it returns an error that it is not a matrix if I try to extract these 2 columns into a matrix mdat <- matrix(date,nox, byrow=TRUE) doesn't work, and search for help did not work, so am posting. Obviously I am a newbee here. Thanks for any help!! Gregory A. Graves Lead Scientist REstoration COoordination and VERification (RECOVER) Division Everglades Restoration Resource Area South Florida Water Management District Phones: DESK: 561 / 681 - 2563 x3730 CELL: 561 / 719 - 8157 [[alternative HTML version deleted]]