How can I invert a Matrix in Objective-C

Asked Oct 02 '14 at 17:37

Active Oct 02 '14 at 17:41

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I am trying to solve a system of equations Ax = b in Objective-C. My A matrix is rectangular by nature so I am trying to find x by doing x = inv(A'*A)*A'*b. I am using vDSP to multiply and transpose the matrices but I need something to invert A'*A and I can't find any function to do that. Also, how am I support to set up my matrix. The size is variable right now I am doing the following and it gives me parameter type warnings.

int numberOfPlays = (int)[playArray count];
int numberOfSignals = (int)[signalMappings count];

float playElements[numberOfPlays][numberOfSignals];
...//set the values of playElements with playElements[i][j] = 2.0 or whatever value
float aTick[numberOfSignals][numberOfPlays];

and then I am using

vDSP_mtrans(*aMatrix, 1 , *aTick, 1, numberOfSignals, numberOfPlays);

edited Oct 02 '14 at 17:41

rmaddy

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asked Oct 02 '14 at 17:37

Blane Townsend

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why are you using `int`s instead of `NSUInteger`? seems like useless casting in this case. – Brad Allred Oct 02 '14 at 19:28
also `NSArray` can only hold objects. you seem to want to store floats in one. – Brad Allred Oct 02 '14 at 19:30
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http://stackoverflow.com/questions/11282746/how-to-perform-matrix-inverse-operation-using-the-accelerate-framework – thelaws Oct 02 '14 at 20:19

How can I invert a Matrix in Objective-C

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