How can I calculate PCA?

edit

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 ();

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

}