# submat¶

## Purpose¶

Extracts a submatrix of a matrix, with the appropriate rows and columns given by the elements of vectors.

## Format¶

y = submat(x, r, c)
Parameters: x (NxK matrix) – data r (LxM matrix) – row indices c (PxQ matrix) – column indices y ((L*M)x(P*Q) matrix) – submatrix of x, y may be larger than x.

## Examples¶

// Create 12x1 vector with consecutive numbers
x = seqa(1, 1, 12);

// Reshape the 12x1 vector into a 3x4 matrix
x = reshape(x, 3, 4);

v1 = { 1 3 };
v2 = { 2 4 };

// Extract sub-matrices
y = submat(x, v1, v2);
z = submat(x, 0, v2);

After the code above, the matrix values are:

1  2  3  4
x = 5  6  7  8
9 10 11 12

y =  2  4
10 12

2  4
z =  6  8
10 12

## Remarks¶

If $$r = 0$$, then all rows of x will be used. If $$c = 0$$, then all columns of x will be used.