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)
I = 
  <float>  - size: [5000 5000]
	Matrix is sparse with 5000 nonzeros
--> full(I(1:10,1:10))
ans = 
  <float>  - size: [10 10]
 
Columns 1 to 10
 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