matlab - c code translation
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Hello, I'm trying to translate my code from Matlab to C in a mex file. But I encoutered some difficulties because Matlab has predefined functiones for almost everything.So this is my Matlab code:
% m=40;
% n=20;
% rap_V = abs(randn(m,n))
% for i = 4:m-3
% for j = 4:n-3
%
% im_A = rap_V(i-3:i+3,j-3:j+3);
% im_A = im_A(:);
And my C code from the mex file:
#include "math.h"
#include "mex.h" //--This one is required
void mexFunction(int nlhs, mxArray *plhs[], int nrhs, const mxArray *prhs[])
{
//Declarations
mxArray *xData;
double *xValues, *outArray;
int i,j,ii,jj,iii;
int rowLen, colLen;
//Copy input pointer x
xData = prhs[0];
//Get matrix x
xValues = mxGetPr(mxGetPr(xData));
rowLen = mxGetN(xData);
colLen = mxGetM(xData);
//Allocate memory and assign output pointer
plhs[0] = mxCreateDoubleMatrix(7*7, 1, mxREAL); //mxReal is our data-type
//Get a pointer to the data space in our newly allocated memory
outArray = mxGetPr(plhs[0]);
//Copy matrix while multiplying each point by 2
for(i=4;i<rowLen-3;i++)
{
for(j=4;j<colLen-3;j++)
{ int con=0;
for(ii=i-3; ii<=i+3; ii++)
for(jj=j-3; jj<=j+3; jj++)
{outArray[con] = xValues[(ii*7)+jj];
con=con+1;
}
}
}
My main problem is this line :
outArray[con] = xValues[(ii*7)+jj];
because it doesn't copy the right values of the input matrix into the 49*1 outArray. The aim is to copy the 7*7 matrixes into a 49*1 which I should use further on in my project. Any ideeas? }
1 个评论
Jan
2011-11-22
Please apply a proper code formatting as explained in the "Markup help" link on this page. Currently your code is not readable.
回答（2 个）
Titus Edelhofer
2011-11-22
Hi,
note that MATLAB sorts the values by column, i.e., you should use
xValues[rowLen*jj+ii]
instead.
Titus
Jan
2011-11-22
This is one mexGetPr to much:
double *xValues;
mxArray *xData;
xData = prhs[0];
// xValues = mxGetPr(mxGetPr(xData)); % ERROR
xValues = mxGetPr(xData);
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2011-11-22
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