Odds ratios from lrm plot
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