R help - Oct 2004 - call step inside a function

I am wondering why my function works fine in R1.7.1 and R1.8.1 but not in 
R1.9.0. I thought it's an environment related problem but I can't solve
it.
>data
   weta jd
1     1  4
2     2 13
3     2 13
4     6  4
5     1  3
6     1  7
7     2 10
8     3 10
9     1  8
10    1  8
11    3  6
12    1  9
13    1  5
14    1  1
15    3 13
16    1  2
17    2  2
18    7 11
19    1  3
20    5  4
21    1  6
22    4  9
23    1  6
24    4  5
25    5  5
26    2  6
> program
function(dataset)
{
        tmp<-glm(weta~1, family=poisson, data=dataset)
        tmp.f<-step(tmp,~.+jd)    
}

When I run program(data) in 1.9.0, an error message appears:

Error in model.frame.default(formula = WETA ~ jd, data = dataset, 
drop.unused.levels = TRUE) :
        Object "dataset" not found


Thanks for help in advance!

Weihong Zeng
University of Albert

weihong wrote:
> I am wondering why my function works fine in R1.7.1 and R1.8.1 but not in 
> R1.9.0. I thought it's an environment related problem but I can't
solve it.
> 
> 
>>data
> 
>    weta jd
> 1     1  4
> 2     2 13
> 3     2 13
> 4     6  4
> 5     1  3
> 6     1  7
> 7     2 10
> 8     3 10
> 9     1  8
> 10    1  8
> 11    3  6
> 12    1  9
> 13    1  5
> 14    1  1
> 15    3 13
> 16    1  2
> 17    2  2
> 18    7 11
> 19    1  3
> 20    5  4
> 21    1  6
> 22    4  9
> 23    1  6
> 24    4  5
> 25    5  5
> 26    2  6
> 
> 
>>program
> 
> function(dataset)
> {
>         tmp<-glm(weta~1, family=poisson, data=dataset)
>         tmp.f<-step(tmp,~.+jd)    
> }
> 
> When I run program(data) in 1.9.0, an error message appears:
> 
> Error in model.frame.default(formula = WETA ~ jd, data = dataset, 
> drop.unused.levels = TRUE) :
>         Object "dataset" not found
> 
> 
> Thanks for help in advance!
> 
> Weihong Zeng
> University of Albert
> 
This is a scoping problem. There may be better answers but the following 
trick has worked for me in the past:

f <- function(z) {
   eval(substitute(fit <- glm(weta ~ 1, family = poisson, data = z),
                   list(z = z)))
   step(fit, ~ . + jd)
}

--sundar

On Mon, 4 Oct 2004, weihong wrote:
>> program
> function(dataset)
> {
>        tmp<-glm(weta~1, family=poisson, data=dataset)
>        tmp.f<-step(tmp,~.+jd)
> }
>
> When I run program(data) in 1.9.0, an error message appears:
>
> Error in model.frame.default(formula = WETA ~ jd, data = dataset,
> drop.unused.levels = TRUE) :
>        Object "dataset" not found
Yes, it looks as though add1.glm is not putting the environment 
information in the same place that model.frame.glm is looking for it.

add1.glm sets up an empty shell of a glm object and calls model.frame.glm, 
but model.frame.glm uses the $terms component to specify the environment, 
and add1.glm doesn't give a $terms component.  Presumably at some time in 
the past model.frame.glm used the $call$formula  component instead.


 	-thomas