How to get percentile of each element of list of matrices

Question

If I have a list of matrices with same dimensions, how can I get each element of list of matrices in R? For example, I have 4 matrices:

> a
           [,1]       [,2]       [,3]
[1,] -0.8761453  0.2821336 -0.8541406
[2,] -0.9649200  1.7734091 -1.2058440
[3,] -0.4250063 -0.8197162 -1.3997540
> b
           [,1]       [,2]       [,3]
[1,] -1.2096577 -0.5440074  0.6102016
[2,] -0.1299645 -0.8943189 -1.8042720
[3,]  1.0111488  0.2547343  0.2395172
> c
           [,1]       [,2]       [,3]
[1,]  0.2853833 -0.2716714  0.2330467
[2,] -0.7963095 -1.2120779  0.6909755
[3,]  0.3479346  0.1803124 -0.7400176
> d
             [,1]       [,2]       [,3]
[1,] -1.048740842 -1.0492152 -0.6889409
[2,] -0.004154795 -0.6167335 -0.8028550
[3,] -1.111915258 -2.1586534 -0.1448612

The result I want is if I want the 2nd least minimum of each element.

> res
           [,1]       [,2]       [,3]
[1,] -1.0487408 -0.5440074 -0.6889409
[2,] -0.7963095 -0.8943189 -1.2058440
[3,] -0.4250063 -0.8197162 -0.7400176

Answer 1

If we need the second minimum value, create an array by concatenating the matrixes together, specify the dimensions and use apply with the required MARGIN, sort the elements from smallest to largest and get the second element

apply(array(c(a, b, c, d), c(dim(a), 4)), c(1, 2), FUN = function(x) sort(x)[2])
#           [,1]       [,2]       [,3]
#[1,] -1.0487408 -0.5440074 -0.6889409
#[2,] -0.7963095 -0.8943189 -1.2058440
#[3,] -0.4250063 -0.8197162 -0.7400176

NOTE: Based on the OP's post, it looks like 'a', 'b', 'c', 'd' are separate matrix objects in the global environment