How can I calculate PCA?

[nihad]

I am trying to use PCA, but it gives memory access violation error. Here is my sample code.

int main(...)
{
.................
vector<float>input_array;

    for(i=0;i<number_of_lines;i++)
    {
        for(j=0;j<feature_vector_size;j++)
        {
            input_array.push_back(read_feature[i][j]);  
        }

        Mat input_feature_vector(input_array);

        Mat projection_result;


        PCA pca(input_feature_vector,Mat(),CV_PCA_DATA_AS_ROW, 0);/////error memory access

        pca.project(input_feature_vector,projection_result);

        for(k=0;k<feature_vector_size;k++)
        {

           fprintf(pca_output_file,"%lf ",projection_result.at <float>(k,0));


        }

                 fprintf(pca_output_file,"\n");
        input_array.clear ();

    }
.............

}

[2kaud]

In cases like this, there is a little known but extremely effective set of steps used by gurus to deal with the situation.

The steps are
1) Use the debugger to find the problem
2) Find the problem using the debugger
3) Follow all the steps