Iden

iden
Computes a sparse or full identity matrix
Other toolboxes required	none
Function category	Helper functions

iden is a function that computes the identity matrix of the desired size, which is either full or sparse.

Syntax

• ID = iden(DIM,SP)

Argument descriptions

• DIM: The number of rows (or equivalently, columns) that ID will have.
• SP: A flag (either 1 or 0) indicating whether ID should or should not be sparse.

Examples

Full and sparse versions of the 2-by-2 identity matrix:

>> iden(2,0)
 
ans =
 
     1     0
     0     1
 
>> iden(2,1)
 
ans =
 
   (1,1)        1
   (2,2)        1

Notes

This function is only meant to simplify code within other functions. If you always want either the full or the sparse identity matrix, just use MATLAB's built-in eye or speye function.

Source code

Click on "expand" to the right to view the MATLAB source code for this function.

1. %%  IDEN  Computes a sparse or full identity matrix

2. %   This function has two required arguments:

3. %     DIM: the number of rows (or columns) of the identity matrix

4. %     SP: a flag (1 or 0)

5. %

6. %   ID = iden(DIM,SP) returns the DIM-by-DIM identity matrix. If SP = 0

7. %   then ID will be full. If SP = 1 then ID will be sparse.

8. %

9. %   Only use this function within other functions to easily get the correct

10. %   identity matrix. If you always want either the full or the sparse

11. %   identity matrix, just use MATLAB's built-in eye or speye function.

12. %

13. %   URL: http://www.qetlab.com/iden

15. %   requires: nothing

16. %   author: Nathaniel Johnston (nathaniel@njohnston.ca)

17. %   package: QETLAB

18. %   last updated: November 28, 2012

20. function id = iden(dim,sp)

22. if(sp)

23.     id = speye(dim);

24. else

25.     id = eye(dim);

26. end