[R] function

Sarah Goslee sarah.goslee at gmail.com
Wed May 12 19:34:38 CEST 2010

I missed the original query, but here am replying to the respondent.

On Wed, May 12, 2010 at 1:28 PM, Daniel Malter <daniel at umd.edu> wrote:
> There is too little information to answer your question definitively.
> However, an obvious reason is that you want to apply the function over
> columns of a data.frame, which is done with apply(), but you try to apply
> the function over elements of a list using lapply(). A list is not a
> data.frame and vice versa, which would be a good reason for your function to
> fail.

Ah, but a dataframe is a list.

To use your example:
> data=data.frame(y=rnorm(100),x=rnorm(100),e=rnorm(100)) # calling your data "data" is a bad idea!
> typeof(data)
[1] "list"
> is.data.frame(data)
[1] TRUE
> is.list(data)
[1] TRUE

> The below example works:
> data=data.frame(y=rnorm(100),x=rnorm(100),e=rnorm(100))
> f=function(x){quantile(x,probs=0.25)}
> apply(data,2,f)

And because a dataframe is a list, so does lapply!

> f=function(x){quantile(x,probs=0.25)}
> apply(data,2,f)
         y          x          e
-0.7412884 -0.6666245 -0.9627692
> lapply(data, f)



R: just when you think you've got a handle on it, you don't.


Sarah Goslee

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