stats mean min max stdev

t9e12.stats.cpp

// t9e12.stats.cpp
// juanfc 2023-11-14
//

#include <iostream>
#include <cmath>
#include <array>
using namespace std;

// consts
const int N=5;

// types
typedef array<float,N> TVec;

// prototypes
void writeArr(TVec a);
void stats(TVec a,
    float& mean, float& min,
    float& max, float& stdev);

int main()
{
    float mean, min, max, stdev;
    TVec a = {{1, 2, 3, 4, 5}};
    writeArr(a); cout << endl;
    stats(a, mean, min, max, stdev);
    cout << "mean: " << mean << endl; // 3
    cout << "min: " << min << endl;   // 1
    cout << "max: " << max << endl;   // 5
    cout << "std dev: " << stdev << endl; // 1.58114

    return 0;
}

void stats(TVec a,
    float& mean, float& min,
    float& max, float& stdev)
{
    mean = 0;
    float sa2 = 0, sa = 0;
    min = max = a[0];
    for (int i = 0; i < N; ++i) {
        mean += a[i];
        sa += a[i];
        sa2 += a[i]*a[i];
        if (a[i] < min) min = a[i];
        else if (a[i] > max) max = a[i];
    }
    mean /= N;
    stdev = sqrt((sa2-sa*sa/N)/(N-1));
}

void writeArr(TVec a)
{
    for (int i = 0; i < N; ++i)
        cout << a[i] << " ";
}

void swap(int& a, int& b)
{
    int t = a;
    a = b; b = t;
}