How can I normalize histogram?

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I want to normalize histogram between 0 and 1. Here is my code segment. It gave all zero output. Your help highly appreciable.

int main()
{
// .....................................
float histogram_sample[1][6]={2.0,2.0,3.0,4.0,1.0,2.0};

    Mat histogram(1,6,CV_32F,(void*)histogram_sample);

    cout<<"Histogram Matrix:"<<histogram<<endl;

    int histSize = 4;
    float start=1.0;
    float end=4.0;
    float range[] = { start,end+1.0 } ;
    const float* histRange = { range };

    bool uniform = true; bool accumulate = false;

    Mat hist;

    calcHist( &histogram, 1, 0, Mat(), hist, 1, &histSize, &histRange, uniform, accumulate );

    cout<<"hist:"<<hist<<endl;

    normalize(hist, hist, 0, 1, NORM_L2, -1, Mat());

    cout<<"Normalize hist:"<<hist<<endl;

}