[R] how to loop through 2 lists with different indexes
jim holtman
jholtman at gmail.com
Wed Sep 6 17:04:27 CEST 2006
To find what names are common to both, use 'intersect'
> x.bin.size <- list('3'=1, '4'=4, '5'=10)
> y.bin.size <- list('2'=4, '3'=42, '4'=253, '5'=954)
> sameNames <- intersect(names(x.bin.size), names(y.bin.size))
> sameNames
[1] "3" "4" "5"
> lapply(sameNames, function(x) sample(seq(y.bin.size[[x]]), x.bin.size[[x]]))
[[1]]
[1] 12
[[2]]
[1] 95 145 228 51
[[3]]
[1] 858 901 630 599 59 196 168 651 364 728
>
On 9/6/06, Tania Oh <tania.oh at brasenose.oxford.ac.uk> wrote:
> Dear all,
>
> I am a newbie in R and need some help please. (I do apologise if my
> email is not as informative as it should be, I've tried to include
> the relevant details without overcrowding it with the rest of the code)
>
> I would like to sample (without replacement) Y objects based on the
> number of objects in X in 5 different bins. I'm having trouble
> because the list object in which the number of objects of X is stored
> in doesn't start its index from 0.
>
> # number of X objects in each of the 5 bins
> x.bin.size <- lapply(x.by.bins, nrow)
>
> x.bin.size
> $`3`
> [1] 1
>
> $`4`
> [1] 3
>
> $`5`
> [1] 10
>
>
> # no. of objects in each of the 5 bins of Y
> y.bin.size <- lapply(y.by.bins, nrow)
>
> > y.bin.size
> $`2`
> [1] 4
>
> $`3`
> [1] 42
>
> $`4`
> [1] 253
>
> $`5`
> [1] 945
>
> how do I loop through Y and sample from X when the index of Y starts
> from 2 and that of X starts from 3? in X, the missing index $`2` is
> assumed to have 0 objects in it. hence, I would only sample from Y
> and X starting from index 3.
>
> sample (y.bin.size$`3`, x.bin.size$`3`, replace=FALSE)
>
> but how should I do this in an R command without knowing which
> indexes (of X ) are empty? Any pointers would be greatly appreciated.
>
>
> Many thanks in advance,
> tania
>
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>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
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