SPEYE Sparse Identity Matrix

Section: Sparse Matrix Support

Usage

Creates a sparse identity matrix of the given size. The syntax for its use is 
  y = speye(m,n)

which forms an m x n sparse matrix with ones on the main diagonal, or 

  y = speye(n)

which forms an n x n sparse matrix with ones on the main diagonal. The matrix type is a float single precision matrix.

Example

The following creates a 5000 by 5000 identity matrix, which would be difficult to do using sparse(eye(5000)) because of the large amount of intermediate storage required. 
--> I = speye(5000);
--> which I
Function I is unknown!
--> full(I(1:10,1:10))

ans = 
 1 0 0 0 0 0 0 0 0 0 
 0 1 0 0 0 0 0 0 0 0 
 0 0 1 0 0 0 0 0 0 0 
 0 0 0 1 0 0 0 0 0 0 
 0 0 0 0 1 0 0 0 0 0 
 0 0 0 0 0 1 0 0 0 0 
 0 0 0 0 0 0 1 0 0 0 
 0 0 0 0 0 0 0 1 0 0 
 0 0 0 0 0 0 0 0 1 0 
 0 0 0 0 0 0 0 0 0 1