Re: [R] Relative Risk in logistic regression

2013-02-03 Thread David Winsemius
On Feb 3, 2013, at 8:15 AM, aminreza Aamini wrote: Dear Coleagues , As my friend John mentined,* the measure of association from a logistic regression is the odds ratio, not the relative risk*. but the point is in follow-up studies, it is commonly preferred to estimate a risk ratio rathe

Re: [R] Relative Risk in logistic regression

2013-02-03 Thread John Sorkin
Amin, It is incorrect to use the relative risk as a measure of association in a logistic regression. The measure of association in a logistic regression is the odds ratio. The odds ratio is an approximation of the relative risk. The approximation becomes progressively better as the disease beco

Re: [R] Relative Risk in logistic regression

2013-02-03 Thread aminreza Aamini
Dear Coleagues , As my friend John mentined,* the measure of association from a logistic regression is the odds ratio, not the relative risk*. but the point is in follow-up studies, it is commonly preferred to estimate a risk ratio rather than an odds ratio. Thats why im looking for RR in logistic

Re: [R] Relative Risk in logistic regression

2013-02-03 Thread Michael Dewey
At 10:49 30/01/2013, aminreza Aamini wrote: Hi all, I am very grateful to all those who write to me 1) how i can obtain relative risk (risk ratio) in logistic regression in R. @TECHREPORT{lumley06, author = {Lumley, T and Kronmal, R and Ma, S}, year = 2006, title = {Relative risk regres

Re: [R] Relative Risk in logistic regression

2013-02-01 Thread Greg Snow
Ivan, In reference to your part 2), in 1989 Li and Duan published a paper where they examined the effect of using the "wrong" link function ( http://projecteuclid.org/DPubS?service=UI&version=1.0&verb=Display&handle=euclid.aos/1176347254). The short version is that they found that in common model

Re: [R] Relative Risk in logistic regression

2013-02-01 Thread Ivan-K
Dear colleagues, I have 2 points: One opinion and one question. 1) In one paper in a peer-reviewed journal, I read about the idea of using a logit regression as a surrogate for the log-binomial, just adding the numerator to the denominator ... It’s tempting to immediately get the RR instead of OR

Re: [R] Relative Risk in logistic regression

2013-01-31 Thread Frank Harrell
I am curious why one would want risk ratios. Unlike odds ratios, they are not interpretable without reference to the base risk. For example a risk ratio of 2 cannot possibly apply to anyone with a starting risk exceeding 1/2. I think it is most helpful to use one of the existing nomograms to sho

Re: [R] Relative Risk in logistic regression

2013-01-30 Thread David Winsemius
On Jan 30, 2013, at 5:49 AM, aminreza Aamini wrote: Hi all, I am very grateful to all those who write to me 1) how i can obtain relative risk (risk ratio) in logistic regression in R. 2) how to obtain the predicted risk for a certain individual using fitted regression model in R. You ob

Re: [R] Relative Risk in logistic regression

2013-01-30 Thread Kevin E. Thorpe
: > > Relative risk = exp(coef(model)) > > > > Only if you fit using the log link. Using the logit link, this gives > odds ratios. > > > --- On Wed, 30/1/13, aminreza Aamini wrote: > > > > > > From: aminreza Aamini > >

Re: [R] Relative Risk in logistic regression

2013-01-30 Thread John Sorkin
he logit link, this gives > odds ratios. > > > --- On Wed, 30/1/13, aminreza Aamini wrote: > > > > > > From: aminreza Aamini > > Subject: [R] Relative Risk in logistic regression > > To: "R-help" > > Date: Wednesday, 30 Januar

Re: [R] Relative Risk in logistic regression

2013-01-30 Thread Kevin E. Thorpe
ative risk = exp(coef(model)) > Only if you fit using the log link. Using the logit link, this gives odds ratios. > --- On Wed, 30/1/13, aminreza Aamini wrote: > > > From: aminreza Aamini > Subject: [R] Relative Risk in logistic regression > To: "R-help" &g

Re: [R] Relative Risk in logistic regression

2013-01-30 Thread John Sorkin
:02 AM, nalluri pratap wrote: > Relative risk = exp(coef(model)) > Only if you fit using the log link. Using the logit link, this gives odds ratios. > --- On Wed, 30/1/13, aminreza Aamini wrote: > > > From: aminreza Aamini > Subject: [R] Relative Risk in logistic regression > To:

Re: [R] Relative Risk in logistic regression

2013-01-30 Thread Kevin E. Thorpe
On 01/30/2013 09:02 AM, nalluri pratap wrote: Relative risk = exp(coef(model)) Only if you fit using the log link. Using the logit link, this gives odds ratios. --- On Wed, 30/1/13, aminreza Aamini wrote: From: aminreza Aamini Subject: [R] Relative Risk in logistic regression To: &q

Re: [R] Relative Risk in logistic regression

2013-01-30 Thread nalluri pratap
up) lm.D90 <- lm(weight ~ group - 1)   prediction_error= lm.D90$residuals --- On Wed, 30/1/13, aminreza Aamini wrote: From: aminreza Aamini Subject: [R] Relative Risk in logistic regression To: "R-help" Date: Wednesday, 30 January, 2013, 4:19 PM Hi all, I am very grateful to all thos

Re: [R] Relative Risk in logistic regression

2013-01-30 Thread nalluri pratap
Relative risk = exp(coef(model)) --- On Wed, 30/1/13, aminreza Aamini wrote: From: aminreza Aamini Subject: [R] Relative Risk in logistic regression To: "R-help" Date: Wednesday, 30 January, 2013, 4:19 PM Hi all, I am very grateful to all those who write to me 1) how i  c

[R] Relative Risk in logistic regression

2013-01-30 Thread aminreza Aamini
Hi all, I am very grateful to all those who write to me 1) how i can obtain relative risk (risk ratio) in logistic regression in R. 2) how to obtain the predicted risk for a certain individual using fitted regression model in R. Many thanks, in advance, for your help. Amin. __

[R] Relative Risk in logistic regression

2013-01-30 Thread aminreza Aamini
Hi all, I am very grateful to all those who write to me 1) how i can obtain relative risk (risk ratio) in logistic regression in R. 2) how to obtain the predicted risk for a certain individual using fitted regression model in R. Many thanks, in advance, for your help. Amin. ___