I have created list of objects in R as follows:
set.seed(1234)
data <- matrix(rnorm(3*4,mean=0,sd=1), 3, 4)
results <- lapply(1:ncol(data), function(i) outer(data[, i], data[, i]))
all 4 list objects have dim=3x3. I also have the following matrix matr <- matrix(c(2,4,6,8),ncol=4), where each value corresponds to the above list objects.
Then, I use this equation matr[,1]*matr[,2]*results[[1]]*results[[2]] between the first two objects in order to create the below matrix
[,1] [,2] [,3]
[1,] 64.135122 2.6966755 12.4307531
[2,] 2.696676 0.1133865 0.5226732
[3,] 12.430753 0.5226732 2.4093448
How can I calculate the above equation for all all possible object combinations and save them to a new list?
>Solution :
We can use combn to create pairwise combination on the sequence of the list, extract the elements and do the multiplication
new_lst <- combn(seq_along(results), 2, \(i) matr[,i[1]] * matr[,i[2]] *
results[[i[1]]] * results[[i[2]]], simplify = FALSE)
names(new_lst) <- combn(seq_along(results), 2, paste, collapse="_")
-output
> new_lst
$`1_2`
[,1] [,2] [,3]
[1,] 64.135122 2.6966755 12.4307531
[2,] 2.696676 0.1133865 0.5226732
[3,] 12.430753 0.5226732 2.4093448
$`1_3`
[,1] [,2] [,3]
[1,] 5.775451 -1.2624981 -5.095849
[2,] -1.262498 0.2759787 1.113939
[3,] -5.095849 1.1139391 4.496217
$`1_4`
[,1] [,2] [,3]
[1,] 18.46710 -2.275650 -18.610758
[2,] -2.27565 0.280422 2.293352
[3,] -18.61076 2.293352 18.755530
$`2_3`
[,1] [,2] [,3]
[1,] 43.621251 -7.589849 -9.242303
[2,] -7.589849 1.320590 1.608108
[3,] -9.242303 1.608108 1.958223
$`2_4`
[,1] [,2] [,3]
[1,] 139.47970 -13.680683 -33.754187
[2,] -13.68068 1.341852 3.310735
[3,] -33.75419 3.310735 8.168537
$`3_4`
[,1] [,2] [,3]
[1,] 12.560327 6.404863 13.837154
[2,] 6.404863 3.266019 7.055953
[3,] 13.837154 7.055953 15.243778