apply function to elements over a list
Sorry for the simple question but I can't think of a good way to take functions elements of a list of data frames. I am sure there is something within the plyr/reshape2 packages but I just can't think of it.
For example I have a list A as follows:
>A
[[1]]
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 1 1 1 1 1 1 1 1 1 1
[2,] 1 1 1 1 1 1 1 1 1 1
[3,] 1 1 1 1 1 1 1 1 1 1
[4,] 1 1 开发者_Python百科 1 1 1 1 1 1 1 1
[5,] 1 1 1 1 1 1 1 1 1 1
[[2]]
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 2 2 2 2 2 2 2 2 2 2
[2,] 2 2 2 2 2 2 2 2 2 2
[3,] 2 2 2 2 2 2 2 2 2 2
[4,] 2 2 2 2 2 2 2 2 2 2
[5,] 2 2 2 2 2 2 2 2 2 2
Say I want to take the mean across the corresponding elements of the matrices in the list. One way to do this would be
Reduce("+",A)/length(A)
I can't seem to feed Reduce()
more complex functions and assume there is a better way in general.
In this case, maybe you're better off with your data in an array
rather than a list?
#Recreate data
A <- list(a=matrix(1,5,10),b=matrix(2,5,10))
#Convert to array
A1 <- array(do.call(cbind,A),dim = c(5,10,2))
#Better way to convert to array
require(abind)
A1 <- abind(A,along = 3)
#Now we can simply use apply
apply(A1,c(1,2),mean)
Maybe do.call
?
do.call(`+`, A)/length(A)
Or if you really don't want to abind
it into a larger matrix,
array(sapply(seq_along(A[[1]]), function(i) mean(sapply(A,`[`,i))),
dim=dim(A[[1]]))
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