[R] how to combine data of several csv-files

[Antje]

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