Continuing with Daniel's example, but with different data values
a <- sample(24)
a
dim(a) <- c(3,4,2)
a
as.vector(a)
## for an array with
## dim(a) == c(3,4,2)
## a[i,j,k] means select the element in position
## i + (j-1)*3 + (k-1)*3*4
index <- function(i,j,k) {
i + (j-1)*3 + (k-1)*3*4
}
## find the vector position described by row 2, column 1, layer 2
index(2,1,2) ## this is the position in the original vector
a[2,1,2] ## this is the value in that position with 3D indexing
a[index(2,1,2)] ## this is the same value with 1D vector indexing
a[14] ## this is the same value with 1D vector indexing
## find the position in row 3, column 4, layer 1
index(3,4,1) ## this is the position in the original vector
a[3,4,1] ## this is the value in that position with 3D indexing
a[index(3,4,1)] ## this is the same value with 1D vector indexing
a[12] ## this is the same value with 1D vector indexing
index(1,1,1) ## this is the position in the original vector
index(2,1,1) ## this is the position in the original vector
index(3,1,1) ## this is the position in the original vector
index(1,2,1) ## this is the position in the original vector
index(2,2,1) ## this is the position in the original vector
index(3,2,1) ## this is the position in the original vector
index(1,3,1) ## this is the position in the original vector
index(2,3,1) ## this is the position in the original vector
index(3,3,1) ## this is the position in the original vector
index(1,4,1) ## this is the position in the original vector
index(2,4,1) ## this is the position in the original vector
index(3,4,1) ## this is the position in the original vector
index(1,1,2) ## this is the position in the original vector
index(2,1,2) ## this is the position in the original vector
index(3,1,2) ## this is the position in the original vector
index(1,2,2) ## this is the position in the original vector
index(2,2,2) ## this is the position in the original vector
index(3,2,2) ## this is the position in the original vector
index(1,3,2) ## this is the position in the original vector
index(2,3,2) ## this is the position in the original vector
index(3,3,2) ## this is the position in the original vector
index(1,4,2) ## this is the position in the original vector
index(2,4,2) ## this is the position in the original vector
index(3,4,2) ## this is the position in the original vector
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