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Matrix Multiplication using arrays (Read 476 times)
firefox950
Matrix Multiplication using arrays
Mar 30th, 2008, 8:17am  

i need help with simple matrix multiplication code in Processing
am using this code.

int[][] matrixA = {{3,2,-1},{0,4,6}};
int[][] matrixB= {{1,0},{5,3},{6,4}};
int[][] matrixC;


void setup()
{

 
  for(int i=0; i<2; i++){
 for(int j=0; j<2; j++){
     for(int k=0; k<3; k++){
     
     
  matrixC[i][j]= matrixC[i][j]+ matrixA[i][k] * matrixB[k][j];
   
     }
 }
  }
}

 
it gives me the error

java.lang.NullPointerException at temporary_8356_2317.setup(Temporary_8356_2317.java:32)
at processing.core.PApplet.handleDisplay(PApplet.java:1390)
at processing.core.PGraphics.requestDisplay(PGraphics.java:690)
at processing.core.PApplet.run(PApplet.java:1562)
at java.lang.Thread.run(Unknown Source)
pleas help
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st33d
Re: Matrix Multiplication using arrays
Reply #1 - Mar 30th, 2008, 12:38pm  
MatrixC needs to be initialised to a specific size before you can use it.

int [][] matrixC = new int[2][2];

And would you mind not double posting please?
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« Last Edit: Mar 30th, 2008, 6:52pm by st33d »  
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