# CrossMatrix

CrossMatrix[r]

gives a matrix whose elements are 1 in a centered cross-shaped region that extends r positions along each index direction, and are 0 otherwise.

CrossMatrix[r,w]

gives a w×w matrix containing a cross-shaped region of 1s.

CrossMatrix[{r1,r2,},]

yields an array whose elements are 1 in a centered cross-shaped region that extends ri positions in the i index direction.

# Details • The cross of 1s is always at the center of the region.
• In CrossMatrix[r] or CrossMatrix[{r1,}] the matrix or array is sized so as to just include all nonzero elements.
• CrossMatrix[All,w] gives a w×w matrix containing a cross shape that is as large as possible.
• CrossMatrix[,{w1,w2,}] gives a w1×w2× array.
• CrossMatrix[{r1,,rn},w] gives a w××w array.
• CrossMatrix[All,{w1,,wn}] gives a w1××wn array containing a cross-shaped region that is as large as possible.
• Elements of CrossMatrix[r] are 1 if their edit distance from the center is not more than 1.
• The parameter r need not be an integer; in an odd-dimensional array, the cross extends Floor[Abs[r+1/2]] pixels from the origin.
• The lines of the cross have width 1 if the corresponding dimension is odd and width 2 otherwise.
• For integer r, CrossMatrix[r] yields a (2r+1)×(2r+1) matrix.

# Examples

open allclose all

## Basic Examples(1)

This computes and plots a cross matrix:

## Scope(5)

Create a rectangular cross matrix:

Specify the matrix size:

Extend the cross to the boundaries of the matrix:

Automatically choose an odd width to just fit the cross:

Extend the cross to the given width and automatically choose the height: