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Generalized Array Operations

13 Mar 2006 (Updated 15 Mar 2006)

Computes generalized array operations by expanding singleton dimensions.

File Information

Description

Computes functions of arrays where the singleton dimensions of each have been expanded to be the size of the other, without actually copying any data.

For example,

  x = rand(4,3,1,2);
  y = rand(4,1,5,2);
  z = genop(@times,x,y);

size(z) will be [4 3 5 2].

Acknowledgements

This submission has inspired the following:
bsxfun substitute

MATLAB release

MATLAB 7.0.4 (R14SP2)

Tags for This File
Everyone's Tags	array, bsxfun, generalized, matrices, matrix manipulation, repmat, singleton
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Comments and Ratings (4)
14 Mar 2006	a user	Code gives error at line 75 when the function handle passed to the function returns a logical rather then a single, double, or integer.
15 Mar 2006	Douglas Schwarz	Comment by "A User" traces back to a limitation of the zeros function. I made changes to work around that and genop should work with logical functions now (as soon as the file gets updated).
23 Nov 2007	Emmanuel FARHI	Absolutely perfect !
27 Dec 2008	Paolo de Leva	An excellent "hack", a smart and computationally efficient algorithm. It is equivalent to BSXFUN (a builtin function introduced about a year later in MATLAB R2007a), and of course much slower, but it can be used as a replacement for BSXFUN by those who have earlier versions of MATLAB. This allowed me to ensure backward compatibility for version 2.0 of my MULTIPROD function, a generalization to N dimensions of the matrix product MTIMES (I am debugging it, I will publish it ass soon as it is ready): http://www.mathworks.fr/matlabcentral/fileexchange/8773 MULTIPROD uses BSXFUN to implement singleton expansion and to increase computational speed. There's another file in MATLAB Central File Exchange which does approximately the same job as GENOP (and perhaps more quickly), but does it less efficiently as for memory usage, by temporarily allocating a huge amount of additional memory to physically expand the arrays: http://www.mathworks.com/matlabcentral/fileexchange/18685

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Updates
15 Mar 2006	fixed documentation typo
15 Mar 2006	Modified so it works with a function returning logical.

Tag Activity for this File
Tag	Applied By	Date/Time
matrices	Douglas Schwarz	22 Oct 2008 08:18:19
array	Douglas Schwarz	22 Oct 2008 08:18:20
repmat	Douglas Schwarz	22 Oct 2008 08:18:20
matrix manipulation	Douglas Schwarz	22 Oct 2008 08:18:20
singleton	Douglas Schwarz	22 Oct 2008 08:18:20
generalized	Douglas Schwarz	22 Oct 2008 08:18:20
bsxfun	Paolo de Leva	27 Dec 2008 08:05:40

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