Thank you Simon, Yes this was in the library(car). There were no negative values in the scatterplot graph or negative limits displayed.
Q-2 Are you sure the lines from the scatterplot are not this?: solid green line: linear regression solid red line: non-linear regression upper dashed red line: upper limits 75 percentile lower dashed red line: lower limits 25 percentile Q-3 I am trying to make a trellis of linear regressions but unsuccessful . I want 3 windows displaying 3 events of linear regression (two-way interactions). I have been trying this: require(lattice) > library(lattice) > trellis.par.set(col.whitebg()) > scatterplot(DevelopIndex~Veg|Aeventexhumed, + xlab = "Distance to vegetation border", + ylab = "Embryonic development index") Error in eval(expr, envir, enclos) : object 'DevelopIndex' not found This error appears and I am not able to produce the trellis of 3 windows displaying 3 events of linear regressions. Please advise Thank you, Jean -- View this message in context: http://r.789695.n4.nabble.com/Q-scatterplot-plot-function-trellis-linear-regressions-tp4630562p4630643.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.