Re: [R] 95% confidence intercal with glm

2010-09-29 Thread Sam
Thats great thanks very much for your help On 29 Sep 2010, at 17:30, Ben Bolker wrote: [I'm a little confused: are you "Sam Smith" or "Chris Mcowen" ... ?] This is admittedly a bit confusing, but the best scale on which to compute standard errors is the link scale. It turns out (I hadn't r

Re: [R] 95% confidence intercal with glm

2010-09-29 Thread Ben Bolker
[I'm a little confused: are you "Sam Smith" or "Chris Mcowen" ... ?] This is admittedly a bit confusing, but the best scale on which to compute standard errors is the link scale. It turns out (I hadn't realized this) that predict.glm does give you not-crazy answers when you ask for se.fit=T

[R] 95% confidence intercal with glm

2010-09-29 Thread Sam
Dear List and Ben ( I apologise if this has been sent twice, but it is not showing in my sent folder and i have been having trouble with my email of late) Right, that makes sense, thanks The reason i used type= response was i wanted to convert the predicted probabilities to the response scale,

Re: [R] 95% confidence intercal with glm

2010-09-29 Thread Chris Mcowen
Right, that makes sense, thanks The reason i used type= response was i wanted to convert the predicted probabilities to the response scale, as surely this is the scale at which a 95CI value is most useful for? I.e >> pp <- predict(model1,se.fit=TRUE, type = "response") 1 0.68 Probability

Re: [R] 95% confidence intercal with glm

2010-09-29 Thread Ben Bolker
On 10-09-29 10:04 AM, Sam wrote: > Hi Ben and list, > > Sorry to be a pain! I have followed your code, and modified it - > **You should not use type="response" here.** The point is that the (symmetric) confidence intervals are computed on the link/linear predictor scale, and then inverse-link-

Re: [R] 95% confidence intercal with glm

2010-09-29 Thread Sam
Hi Ben and list, Sorry to be a pain! I have followed your code, and modified it - > pp <- predict(model1,se.fit=TRUE, type = "response") >> etaframe <- > + with(pp,cbind(fit,lower=fit-1.96*se.fit,upper=fit+1.96*se.fit)) >> pframe <- plogis(etaframe) >> pframe My response variable is 0 or 1, the

Re: [R] 95% confidence intercal with glm

2010-09-29 Thread Sam
Hi Ben and list, Sorry to be a pain! I have followed your code, and modified it - > pp <- predict(model1,se.fit=TRUE, type = "response") >> etaframe <- > + with(pp,cbind(fit,lower=fit-1.96*se.fit,upper=fit+1.96*se.fit)) >> pframe <- plogis(etaframe) >> pframe My response variable is 0 or 1, the

Re: [R] 95% confidence intercal with glm

2010-09-29 Thread Ben Bolker
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 ## from ?glm counts <- c(18,17,15,20,10,20,25,13,12) outcome <- gl(3,1,9) treatment <- gl(3,3) d.AD <- data.frame(treatment, outcome, counts) glm.D93 <- glm(counts ~ outcome + treatment, family=poisson, data=d.AD) ## predict on 'link'

Re: [R] 95% confidence intercal with glm

2010-09-29 Thread Sam
I am looking to do the same but am a bit confused > and apply the inverse link function for your model. i understand up to this point and i understand what this means, however i am unsure why it needs to be done and how you do it - i.e i use family="binomial" is this wrong if i use this method

Re: [R] 95% confidence intercal with glm

2010-09-28 Thread Ben Bolker
zozio32 gmail.com> writes: > > > Hi > > I had to use a glm instead of my basic lm on some data due to unconstant > variance. > > now, when I plot the model over the data, how can I easily get the 95% > confidence interval that sormally coming from: > > > yv <- predict(modelVar,list

[R] 95% confidence intercal with glm

2010-09-28 Thread zozio32
Hi I had to use a glm instead of my basic lm on some data due to unconstant variance. now, when I plot the model over the data, how can I easily get the 95% confidence interval that sormally coming from: > yv <- predict(modelVar,list(aveLength=xv),int="c") > matlines(x