[R] Using objects within functions in formulas

[Rui Barradas]

Hello,

Try the following. It uses argument 'data' to pass the data.frame w2. In 
the function below, I've changed the pastes to two lines of code because 
the first one changes the way the formula is put together.

test1 <- function(x2, y2, w2) {
     #print(str(w2))
     p1 <- paste("(1|", names(w2), ")", collapse=" + ", sep="")
     p2 <- paste("y2 ~ x2 +" , p1)
     form = as.formula(p2)
     m1 = glmer(form, data = w2)
     return(m1)
}


Hope this helps,

Rui Barradas
Em 09-01-2013 16:53, Aidan MacNamara escreveu:
> Dear all,
>
> I'm looking to create a formula within a function to pass to glmer()
> and I'm having a problem that the following example will illustrate:
>
> library(lme4)
> y1 = rnorm(10)
> x1 = data.frame(x11=rnorm(10), x12=rnorm(10), x13=rnorm(10))
> x1 = data.matrix(x1)
> w1 = data.frame(w11=sample(1:3,10, replace=TRUE), w12=sample(1:3,10,
> replace=TRUE), w13=sample(1:3,10, replace=TRUE))
>
> test1 <- function(x2, y2, w2) {
>
> 	print(str(w2))
> 	form = as.formula(paste("y2 ~ x2 +" ,paste("(1|w2$", names(w2), ")",
> collapse=" + ", sep="")))
> 	m1 = glmer(form)
> 	return(m1)
> }
>
> model1 = test1(x2=x1, y2=y1, w2=w1)
>
> As can be seen from the print statement within the function, the
> object "w2" is present and is a data frame. However, the following
> error occurs:
>
> Error in is.factor(x) : object 'w2' not found
>
> This can be rectified by making 'w2' global - defining it outside the
> function. I know there are issues with defining formulas and
> environment but I'm not sure why this problem is specific to 'w2' and
> not the other objects passed to the function.
>
> Any help would be appreciated.
>
> Aidan MacNamara
> EMBL-EBI
>
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