Re: [R] glm inside one self-defined function

From: <Bill.Venables_at_csiro.au>
Date: Wed 23 Aug 2006 - 13:54:28 EST


Mike Wolfgang asks:

>
> From: r-help-bounces@stat.math.ethz.ch
[mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Mike Wolfgang
> Sent: Wednesday, 23 August 2006 1:31 PM
> To: R-help list
> Subject: [R] glm inside one self-defined function
>
> Hi list,
>
> I've searched in R-help and found some related discussions but still
could
> not understand this type of error. My own function is pretty complex,
so I
> would not put it here, but the basic algorithm is like this:
> myfun<-function(k){
> mydata<-...#by someway I create a data frame
> mymodel<-glm(y~.,family=binomial(),data=mydata)
> ...#some other stuff
> }

I think you are leaving out something. Here is a test of what you claim gives a problem (R 2.3.1, Windows):

    > myfun <- function(n) {

    +   z <- rnorm(n)
    +   mydata <- data.frame(x = z, 
    +     y = rbinom(n, size = 1, prob = exp(z)/(1+exp(z))))
    +   fm <- glm(y ~ x, binomial, mydata)
    +   fm
    + }

    >
    > myfun(100)     

    Call: glm(formula = y ~ x, family = binomial, data = mydata)     

    Coefficients:

    (Intercept)            x  
    	 0.1587       1.0223  
    
    Degrees of Freedom: 99 Total (i.e. Null);  98 Residual
    Null Deviance:      137.6 
    Residual Deviance: 118.3        AIC: 122.3 

Not even a murmur of complaint. (This also works in S-PLUS 7.0 but earlier versions of S-PLUS gave a problem rather like the one you note, curiously.)

Look again at your code and see if the abstract version you give really matches what you did, may I suggest?

>
> as I execute this function, it gives error like this
> Error in inherits(x, "data.frame") : object "mydata" not found
>
> So I guess glm here tries to find "mydata" in the parent environment.
Why
> doesn't it take "mydata" inside the function? How to let glm correctly
> locate it? Is this (scope/environment) mentioned in R manual? Thanks,
>
> Mike



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