On Mon, 2010-09-20 at 17:31 +0800, elaine kuo wrote: > Dear List, > > > > I ran a regression model using lm and produced a regression line using > abline. > > > The line ranges from -20 to 20 in x axis, > > and the section I only want is from -20 to 0. > > > > Please kindly advise any function in abline () to set the range of x axes.
You can't; these are already set by the plot, and abline only *adds* to the plot. You need to think about this a different way. What you want are the model predictions for points spread over the range (-20, 0]. So set up a new data set of 'x' values and use predict() to generate the appropriate 'y' values. Here's an example: set.seed(123) dat <- data.frame(x = sample(seq(-20, 20, length = 100))) dat <- within(dat, y <- 8 + (1.8 * x) + (10 * rnorm(100))) mod <- lm(y ~ x, data = dat) ## now plot the data plot(y ~ x, data = dat) ## now predict 50 values spread evenly on range (-20, 0] newdat <- data.frame(x = seq(-20, 0, length = 50)) newdat <- within(newdat, ypred <- predict(mod, newdat)) ## add these predictions as a line to the plot lines(ypred ~ x, data = newdat, col = "red", lwd = 2) HTH G > Thank you > > > > Elaine > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. -- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, 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 %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% ______________________________________________ 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.
