Michelle Ensbey
2009-Apr-24 07:03 UTC
[R] prediction intervals (alpha and beta) for model average estimates from binomial glm and model.avg (library=dRedging)
Hi all, I was wondering if there is a function out there, or someone has written code for making confidence intervals around model averaged predictions (y~á+âx). The model average estimates are from the dRedging library? It seems a common thing but I can't seem to find one via the search engines Examples of the models are: fit1 <- glm(y~ dbh, family = binomial, data = data) fit2 <- glm(y~ dbh+vegperc, family = binomial, data = data) fit3 <- glm(y~ dbh, family = binomial, data = data) and the model averaging model.averaging <-model.avg(fit1,fit2,fit3, method="0") and the output (from model.avg) has the following items: Coefficient, Variance, Standard error, adjusted standard error and lower and upper confidence interval for each parameter (and intercept). What I would like to do is make "prediction intervals". I know I need to include covariance and variance. Please let me know if anyone has a function or code to get these prediction intervals out of this output. Thanks in advance for your help, and please advise me if you need more information M michelle.ensbey@nt.gov.au R version 2.8.1 [[alternative HTML version deleted]]
David Winsemius
2009-Apr-24 12:54 UTC
[R] prediction intervals (alpha and beta) for model average estimates from binomial glm and model.avg (library=dRedging)
In R, the predict family of functions provides that facility. If you want the code it will be in the particular function associated with the model type. ?predict ?predict.glm # the example illustrates creation of prediction curves on the response scale for a specific range of data. # create the desired CI's by appropriate use of the se.fit value returned from the predict call. # This is the code inside predict.glm that does the work when se.fit is set as TRUE in the predict call: se.fit <- pred$se.fit switch(type, response = { se.fit <- se.fit * abs(family(object)$mu.eta(fit)) fit <- family(object)$linkinv(fit) }, link = , terms = ) -- David Winsemius On Apr 24, 2009, at 3:03 AM, Michelle Ensbey wrote:> Hi all, > > I was wondering if there is a function out there, or someone has > written code for making confidence intervals around model averaged > predictions (y~?+?x). The model average estimates are from the > dRedging library? > > It seems a common thing but I can't seem to find one via the search > engines > > Examples of the models are: > > fit1 <- glm(y~ dbh, family = binomial, data = data) > > fit2 <- glm(y~ dbh+vegperc, family = binomial, data = data) > > fit3 <- glm(y~ dbh, family = binomial, data = data) > > and the model averaging > > model.averaging <-model.avg(fit1,fit2,fit3, method="0") > > and the output (from model.avg) has the following items: > Coefficient, Variance, Standard error, adjusted standard error and > lower and upper confidence interval for each parameter (and > intercept). > > What I would like to do is make "prediction intervals". I know I > need to include covariance and variance. Please let me know if > anyone has a function or code to get these prediction intervals out > of this output. > > Thanks in advance for your help, and please advise me if you need > more information > > M > michelle.ensbey at nt.gov.au > > R version 2.8.1David Winsemius, MD Heritage Laboratories West Hartford, CT
Michelle Ensbey
2009-Apr-27 07:19 UTC
[R] prediction intervals (alpha and beta) for model average estimates from binomial glm and model.avg (library=dRedging)
Thanks for your swift reply I'm sorry to say that I tried that, and it doesn't appear to work for predicting from the "model.avg" object (ouput). Model.avg is a model averaging function in dRedging. I am NOT trying to predict from the coefficients estimated directly from the glm. For :> fit1 <- glm(y~ dbh, family = binomial, data = data)> fit2 <- glm(y~ dbh+vegperc, family = binomial, data = data)> fit3 <- glm(y~ dbh, family = binomial, data = data)##and the model averaging> model.averaging <-model.avg(fit1,fit2,fit3, method="0")##Then when trying to predict you get the error below I understand it is because it is not a glm (or other compatable object) but I thought maybe someone had come across and solved this problem already so I thought I'd check:> predict(model.averaging)OR> predict(model.averaging,"Patch_Num")Error in UseMethod("predict") : no applicable method for "predict" ##Comes up. Does anyone have a function or code or has done this (for coefficients obtained from the model.avg function) in the past and can give advice. Thanks again for your help, let me know if I've just missed something. Cheers M -----Original Message----- From: David Winsemius [mailto:dwinsemius at comcast.net] Sent: Friday, 24 April 2009 10:24 PM To: Michelle Ensbey Cc: r-help at r-project.org Subject: Re: [R] prediction intervals (alpha and beta) for model average estimates from binomial glm and model.avg (library=dRedging) In R, the predict family of functions provides that facility. If you want the code it will be in the particular function associated with the model type. ?predict ?predict.glm # the example illustrates creation of prediction curves on the response scale for a specific range of data. # create the desired CI's by appropriate use of the se.fit value returned from the predict call. # This is the code inside predict.glm that does the work when se.fit is set as TRUE in the predict call: se.fit <- pred$se.fit switch(type, response = { se.fit <- se.fit * abs(family(object)$mu.eta(fit)) fit <- family(object)$linkinv(fit) }, link = , terms = ) -- David Winsemius On Apr 24, 2009, at 3:03 AM, Michelle Ensbey wrote:> Hi all, > > I was wondering if there is a function out there, or someone has > written code for making confidence intervals around model averaged > predictions (y~?+?x). The model average estimates are from the > dRedging library? > > It seems a common thing but I can't seem to find one via the search > engines > > Examples of the models are: > > fit1 <- glm(y~ dbh, family = binomial, data = data) > > fit2 <- glm(y~ dbh+vegperc, family = binomial, data = data) > > fit3 <- glm(y~ dbh, family = binomial, data = data) > > and the model averaging > > model.averaging <-model.avg(fit1,fit2,fit3, method="0") > > and the output (from model.avg) has the following items: > Coefficient, Variance, Standard error, adjusted standard error and > lower and upper confidence interval for each parameter (and > intercept). > > What I would like to do is make "prediction intervals". I know I > need to include covariance and variance. Please let me know if > anyone has a function or code to get these prediction intervals out > of this output. > > Thanks in advance for your help, and please advise me if you need > more information > > M > michelle.ensbey at nt.gov.au > > R version 2.8.1David Winsemius, MD Heritage Laboratories West Hartford, CT