On Jul 28, 2011, at 4:14 PM, Jonathan Greenberg wrote:
I'm hoping this is an easy problem that I'm missing something
obvious. Given:
x=c(1,1,1,2,2,3,3,3)
y=c(1:length(x))
dataframe=data.frame(x,y)
I would like to convert this to a list for use with certain functions,
where each entry of the list is a subsetted dataframe based on
dataframe$x
?split
> split(dataframe, x)
$`1`
x y
1 1 1
2 1 2
3 1 3
$`2`
x y
4 2 4
5 2 5
$`3`
x y
6 3 6
7 3 7
8 3 8
I can do this "brute force" by a for-next loop:
unique_x=unique(dataframe$x)
unique_x_N=length(unique_x)
dataframe_to_list=vector(mode="list",length=unique_x_N)
for(i in 1:unique_x_N)
{
dataframe_to_list[[i]]=subset(dataframe,x==unique_x[i])
}
My R-gut is telling me there's a much more efficient way of doing this
-- is it right?
--j
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David Winsemius, MD
West Hartford, CT
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