[R] predict.glm & newdata

[Daniel Malter]

Hi,

could it be the "newdata" argument? When I run predict with the newdata
argument, I get an error message - a different one though. The second reason
might be that your dataset is named df, which is defined as a function an
may produce problems. Try renaming the dataset.

yhat=predict(reg1,newdata=x2) 

x1=seq(1:100)           
r.norm1=rnorm(100,0,20) 
x1=r.norm1+x1           
                        
x2=x1*2                 
r.norm2=rnorm(200,0,20) 
x2=r.norm2+x2

reg1=glm(y1~x1,binomial)      
yhat=predict(reg1) 		     ##prediction works fine           
yhat=predict(reg1,newdata=x2) ##gives error message because of "newdata"

>Error in eval(predvars, data, env) : 
  numeric 'envir' arg not of length one

yhat=predict(reg1,data=x2) ##works fine

##using offset

ofst=rep(0.5,100)                    
                                     
reg1=glm(y1~x1,binomial,offset=ofst) 
yhat=predict(reg1)                   
yhat1=predict(reg1,newdata=x2) ##gives error message       
yhat2=predict(reg1,data=x2)      ##works fine               


-------------------------
cuncta stricte discussurus
-------------------------

-----Ursprüngliche Nachricht-----
Von: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] Im
Auftrag von Tom Guston
Gesendet: Friday, April 04, 2008 1:29 PM
An: r-help at r-project.org
Betreff: [R] predict.glm & newdata


Hi all - 

I'm stumped by the following

mdl <- glm(resp ~ . , data = df, family=binomial, offset = ofst) WORKS yhat
<- predict(mdl) WORKS yhat <- predict(mdl,newdata = df) FAILS

Error in drop(X[, piv, drop = FALSE] %*% beta[piv]) : 
  subscript out of bounds


I've tried without offset, quoting binomial. The offset variable ofst IS in
df.

Previous postings indicate possible names(df) problems (renaming factor
levels?) but I'm using the same data.frame for the newdata option.

Thank you in advance for any pointers.

Tom.




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