Iden

From QETLAB
Jump to: navigation, search
iden
Computes a sparse or full identity matrix

Other toolboxes required none
Function category Helper functions
This is a helper function that only exists to aid other functions in QETLAB. If you are an end-user of QETLAB, you likely will never have a reason to use this function.

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
  14.  
  15. %   requires: nothing
  16. %   author: Nathaniel Johnston (nathaniel@njohnston.ca)
  17. %   package: QETLAB
  18. %   last updated: November 28, 2012
  19.  
  20. function id = iden(dim,sp)
  21.  
  22. if(sp)
  23.     id = speye(dim);
  24. else
  25.     id = eye(dim);
  26. end