The code library(Design) f <- lrm(y~x1+x2+x1*x2, data=data) plot(f) produces a plot of log odds vs x2 with 0.95 confidence intervals. How do I get a plot of odds ratios vs x2 instead? Thanks -- View this message in context: http://r.789695.n4.nabble.com/Odds-ratios-from-lrm-plot-tp4033340p4033340.html Sent from the R help mailing list archive at Nabble.com.
The Design package is obsolete. Use its replacement rms - see http://biostat.mc.vanderbilt.edu/Rrms. Use something like the following to reproduce what you already have: To plot odds ratios against a specific value of x2 and at a specific x1, type ?contrast.rms to see examples. Frank RD235 wrote:> > The code > > library(Design) > f <- lrm(y~x1+x2+x1*x2, data=data) > plot(f) > > produces a plot of log odds vs x2 with 0.95 confidence intervals. How do I > get a plot of odds ratios vs x2 instead? > > Thanks >----- Frank Harrell Department of Biostatistics, Vanderbilt University -- View this message in context: http://r.789695.n4.nabble.com/Odds-ratios-from-lrm-plot-tp4033340p4033414.html Sent from the R help mailing list archive at Nabble.com.
On Nov 11, 2011, at 9:08 PM, RD235 wrote:> The code > > library(Design) > f <- lrm(y~x1+x2+x1*x2, data=data) > plot(f) > > produces a plot of log odds vs x2 with 0.95 confidence intervals. > How do I > get a plot of odds ratios vs x2 instead?You would construct a dataset that had selected combinations of x1 and x2 and then plot the "response". It's been a couple of years since I used Design. Harrell migrated to lattice plots when he upgraded to 'rms' and changed the Predict/plot interface a bit. In the new version it might something like plot(predict(f, x1=seq( ...), x2=c(1,2), type= "fitted"), deopending on teh data arrangement. Why don't you look more closely at the help page for `lrm` and work through the examples. At least in the current 'rms' version there is more than one worked example, and I'm pretty sure there were one in Design before that. -- David Winsemius, MD West Hartford, CT