Re: [R] Logistic and Linear Regression Libraries

2009-10-31 Thread David Winsemius
On Oct 31, 2009, at 7:29 AM, tdm wrote: OK, I think I've figured it out, the predict of lrm didn't seem to pass it through the logistic function. If I do this then the value is similar to that of lm. Is this by design? Yes, at least for certain meanings of "this". When working with p

Re: [R] Logistic and Linear Regression Libraries

2009-10-31 Thread Mark Difford
tdm wrote: >> OK, I think I've figured it out, the predict of lrm didn't seem to pass >> it through the logistic >> function. If I do this then the value is similar to that of lm. Is this >> by design? Why would it >> be so? Please take some time to read the help files on these functions so th

Re: [R] Logistic and Linear Regression Libraries

2009-10-31 Thread tdm
OK, I think I've figured it out, the predict of lrm didn't seem to pass it through the logistic function. If I do this then the value is similar to that of lm. Is this by design? Why would it be so? 1 / (1 + Exp(-1 * 3.38)) = 0.967 tdm wrote: > > > Anyway, do you know why the lrm predict g

Re: [R] Logistic and Linear Regression Libraries

2009-10-31 Thread tdm
Hi Bill, Thanks for you comments. You may be right in that my ability to use the software may be the problem. I was using lm to fit a model with 'target' values of 0 or 1. I then discovered there was a lrm model as well, so just replaced lm with lrm and expected it to be fine. Then I found that t

Re: [R] Logistic and Linear Regression Libraries

2009-10-31 Thread Mark Difford
Hi Phil, >> So far for logistic regression I've tried glm(MASS) and lrm (Design) and >> found there is a big >> difference. Be sure that you mean what you say, that you are saying what you mean, and that you know what you mean when making such statements, especially on this list. glm is not in

Re: [R] Logistic and Linear Regression Libraries

2009-10-31 Thread Bill.Venables
glm is not, and never was. part of the MASS package. It's in the stats package. Have you sorted out why there is a "big difference" between the results you get using glm and lrm? Are you confident it is due to the algorithms used and not your ability to use the software? To be helpful, if d