[R] data.frame to array?

[hadley wickham]

On Fri, Apr 3, 2009 at 1:45 PM,  <rkevinburton at charter.net> wrote:
> I have a list of data.frames
>
>> str(bins)
>
> List of 19217
>  $ 100026:'data.frame': 1 obs. of  6 variables:
>  ..$ Sku  : chr "100026"
>  ..$ Bin  : chr "T149C"
>  ..$ Count: int 108
>  ..$ X    : int 20
>  ..$ Y    : int 149
>  ..$ Z    : chr "3"
>  $ 100030:'data.frame': 1 obs. of  6 variables:
> .......
> As you can see one 'column' is "Count". This list seems to contain 19217 data.frames. I would like to create an array of 19217 integers which hold the values of the "Count" column. I have tried the obvious (to me):
>
> bins[[1:3]]$Count
>
> But that returns NULL instead of an array of length 3 that I was expecting. Interestingly bins[[1]]$Count returns the first "Count" in the list of data frames. How do I get all of the "Count"s?

Why not turn your list of data frames into a single data frame?

bindf <- do.call("rbind", bins)
bindf$Count

Hadley

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