[R] Accumulating results from "for" loop in a list/array

[Schalk Heunis]

Steven

I think list() can help you

##########################################
indlist = list()
 for (i in 1:(dim(x)[2]))  {
         indlist[[paste("ind", i, sep = "")]] <-  which(x[ , i] == "y")
 }
accum = unlist(indlist)
print(indlist$ind1)
###########################################

Schalk Heunis



On Fri, Sep 11, 2009 at 7:52 AM, Steven Kang <stochastickang at gmail.com> wrote:
> Dear R users,
>
>
> I would like to accumulate objects generated from 'for' loop to a list or
> array.
>
> To illustrate the problem, arbitrary data set and script is shown below,
>
>
> x <- data.frame(a = c(rep("n",3),rep("y",2),rep("n",3),rep("y",2)), b =
> c(rep("y",2),rep("n",4),rep("y",3),"n"), c = c(rep("n",7),rep("y",3)), d =
> c("y", rep("n",4), rep("y",2), rep("n",3)))
>
> for (i in 1:(dim(x)[2]))  {
>         assign(paste("ind", i, sep = ""), which(x[ , i] == "y"))
>          accum <- c(ind1, ind2, ind3, ind4)
> }
>
>> ind1
> [1]  4  5  9 10
>> ind2
> [1] 1 2 7 8 9
>> ind3
> [1]  8  9 10
>> ind4
> [1] 1 6 7
>> accum
>  [1]  4  5  9 10  1  2  7  8  9  8  9 10  1  6  7
>
> Are there any alternative method where the highlighted statement above can
> be represented without typing individual objects manually? (as it can be
> very tedious with large number of objects; i.e ind1, ind2, ....., ind100)
>
> Also, is there any way to extract individual objects ('ind1' etc) from
> 'accum'?
>
>> accum[1:length(ind1)]
> [1]  4  5  9 10
> gives 'ind1', but this may become messy for other objects (like 'ind10')
>
>
> Highly appreciate for sharing your expertise in solving this problem.
>
>        [[alternative HTML version deleted]]
>
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