# slice.index

0th

Percentile

##### Slice Indexes in an Array

Returns a matrix of integers indicating the number of their slice in a given array.

Keywords
array
##### Usage
slice.index(x, MARGIN)
##### Arguments
x

an array. If x has no dimension attribute, it is considered a one-dimensional array.

MARGIN

an integer vector giving the dimension numbers to slice by.

##### Details

If MARGIN gives a single dimension, then all elements of slice number i with respect to this have value i. In general, slice numbers are obtained by numbering all combinations of indices in the dimensions given by MARGIN in column-major order. I.e., with $m_1$, …, $m_k$ the dimension numbers (elements of MARGIN) sliced by and $d_{m_1}$, …, $d_{m_k}$ the corresponding extents, and $n_1 = 1$, $n_2 = d_{m_1}$, …, $n_k = d_{m_1} \cdots d_{m_{k-1}}$, the number of the slice where dimension $m_1$ has value $i_1$, …, dimension $m_k$ has value $i_k$ is $1 + n_1 (i_1 - 1) + \cdots + n_k (i_k - 1)$.

##### Value

An integer array y with dimensions corresponding to those of x.

row and col for determining row and column indexes; in fact, these are special cases of slice.index corresponding to MARGIN equal to 1 and 2, respectively when x is a matrix.
library(base) # NOT RUN { x <- array(1 : 24, c(2, 3, 4)) slice.index(x, 2) slice.index(x, c(1, 3)) ## When slicing by dimensions 1 and 3, slice index 5 is obtained for ## dimension 1 has value 1 and dimension 3 has value 3 (see above): which(slice.index(x, c(1, 3)) == 5, arr.ind = TRUE) # }