Apply function to a list of lists-CodePudding

I have a list of length 100. Each entry is itself a list containing 31 matrices with 10 rows and five columns.

>length(dati_fault)
[1] 100

> length(dati_fault[[1]])
[1] 31

I should get 100 averages of the variables summarizing the 31 matrices each element of the list

media_1<-list()
for(i in nrow(dati_fault)){
  for(j in nrow(dati_fault[[i]]))
  media_1[[i]]<-lapply(dati_fault, colMeans(j))
  
}
media_1

But I get nothing because the media_1 list remains empty

CodePudding user response：

you don't need for loops to do so. You can directly work with lapply:

lapply(dati_fault, \(x) colMeans(do.call(rbind, x)))

This does the following: for each entry of dati_fault (i.e. each sublist of 31 matrices) these matrices are bound together (using rbind) into one single matrix with 310 rows and 5 columns. Then, colMeans is applied to this matrix.

If you are not familiar with the shorthand notation for anonymous functions (i.e. \(x)) you can read about it here.

CodePudding user response：

sample data

dati_fault <- lapply(1:100, function(x) {
  rep(list(matrix(sample(50, replace = T), nrow = 10, ncol = 5)), 31)
})

case 1: calculate means for each matrix

# to get the colMeans of each matrix (100 * 31 mean vectors)
lapply(dati_fault, function(x) lapply(x, colMeans))

case 2: calculate the mean of all matrixes in same list

# to get the colMeans of all 31 matrixes together (100 mean vectors) 
lapply(dati_fault, function(x) colMeans(do.call(rbind, x)))