This should do it:
> v1 <- NA
> v2 <- rnorm(6)
> v3 <- rnorm(6)
> v4 <- rnorm(6)
> v5 <- rnorm(6)
> v6 <- rnorm(6)
> v7 <- rnorm(6)
> v8 <- rnorm(6)
> v8 <- NA
>
> list <- list(v1,v2,v3,v4,v5,v6,v7,v8)
> categ <- c(NA,"cat1","cat1","cat1","cat2","cat2","cat2",NA)
>
> # create partitioned list
> list.cat <- split(list, categ)
> # combine each partition into a matrix
> list.mat <- lapply(list.cat, function(x) do.call('rbind', x))
> # now take the means of each column
> lapply(list.mat, colMeans)
$cat1
[1] -0.5699080 0.3855693 1.1051809 0.2379324 0.6684713 0.3240003
$cat2
[1] 0.38160462 -0.10559496 -0.40963090 -0.09507354 0.95021406 -0.31491450
>
On 7/30/07, Antje <[EMAIL PROTECTED]> wrote:
> okay, I played a bit around and now I have some kind of testcase for you:
>
> v1 <- NA
> v2 <- rnorm(6)
> v3 <- rnorm(6)
> v4 <- rnorm(6)
> v5 <- rnorm(6)
> v6 <- rnorm(6)
> v7 <- rnorm(6)
> v8 <- rnorm(6)
> v8 <- NA
>
> list <- list(v1,v2,v3,v4,v5,v6,v7,v8)
> categ <- c(NA,"cat1","cat1","cat1","cat2","cat2","cat2",NA)
>
> > list
> [[1]]
> [1] NA
>
> [[2]]
> [1] -0.6442149 -0.2047012 -1.1986041 -0.2097442 -0.7343465 -1.3888750
>
> [[3]]
> [1] 0.02354036 -1.36186952 -0.42197792 1.50445971 -1.76763996 0.53722404
>
> [[4]]
> [1] -1.40362589 0.13045724 -0.84651458 1.57005071 0.06961015 0.25269771
>
> [[5]]
> [1] -1.1829260 2.1411553 -0.1327081 -0.1053442 -0.8179396 -1.2342698
>
> [[6]]
> [1] 1.17099178 0.49248118 -0.18690065 1.50050976 -0.65552410 -0.01243247
>
> [[7]]
> [1] -0.046778203 -0.233788840 0.443908897 -1.649740180 0.003991354
> -0.228020092
>
> [[8]]
> [1] NA
>
> now, I need the means (and sd) of element 1 of list[2],list[3],list[4]
> (because they belong to "cat1") and
>
> = mean(-0.6442149, 0.02354036, -1.40362589)
>
> the same for element 2 up to element 6 (--> I would the get a vector
> containing the means for "cat1")
> the same for the vectors belonging to "cat2".
>
> does anybody now understand what I mean?
>
> Antje
>
> ______________________________________________
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> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
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