Incomplete sheet

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matrix

Create

Action	Code	Details
From vector, as column vector	matrix(x)
From vector, as column vector	cbind(x)
Diagonal matrix from vector	diag(x)
Create vector or matrix, depending on the number of columns	mat.or.vec(x, nc=2)

Test

Action	Code	Details
Is matrix	is.matrix(x)
Is vector (has singleton dimension)	?
Is square matrix	nrow(x) == ncol(x)
Each column contains at most 1 unique value (i.e. all equal)	apply(x, 2, uniqueN) == 1
Check if all rows are equal	all(mat[1,] == t(mat))

Get

Action	Code	Details
Elements by (row,col) pairs	mat[matrix(c(2,3), c(4,5)), ncol=2)]

Convert

Action	Code	Details
To list of row vectors	split(mat, row(mat))
To list of column vectors	split(mat, col(mat))
To list of submatrices grouped by row	lapply(split(mat, rowFactor), matrix, ncol = ncol(mat))