On Thu, 2006-10-12 at 15:41 +0200, Johan A. Stenberg wrote: > Dear list members, > > When I create a simple scatterplot with a regression line (se below) the > line is automatically extrapolated outside the range of data points. Why > is this and how can I prevent R from extrapolating the regression line? > > Thank you in advance, > Johan > > model<-lm(Herb~Para) > plot(Para,Herb) > abline(model)
Hi Johan, Simply predict over the range of your predictor (Para). As I don't have those data, the example below uses dummy data X <- rnorm(500) # dummy data Y <- X + rnorm(500) mod <- lm(Y ~ X) # fit model # regular sequence over range of predictor X newdat <- seq(min(X), max(X), length = 100) # predict Y for each of these new data points pred <- predict(mod, newdata = list(X = newdat)) # plot the results plot(Y ~ X) lines(pred ~ newdat, col = "red") HTH G -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Gavin Simpson [t] +44 (0)20 7679 0522 ECRC & ENSIS, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% ______________________________________________ [email protected] 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.
