C++: Mean Median and Mode

Question

I've recently created a C++ program to find the mean median and mode of an array of values. I realize this would be much better to do within a class. However, my function to generate the mean is not spitting out the right number, although I'm pretty certain the logic is fine.

Also, I was able to modify a snipbit from something I found online to create a function that generates the mode, or at least the 1st most occurring values it can find, that I was able to implement. However, I am not 100% sure of how to wrap my head around what is actually happening within the function.

A better understanding of what is happening in the mode function and what the hell is going wrong in my mean function would be greatly appreciated.

This is my code so far:

#include <iostream>

using namespace std;

void mode(int[], int);
void mean(int[], int);
void sort(int[], int);
void median(int[], int);

int main()
{

   int array[15];
   float total, mode;
   int n = 15;//number of elements in array

    //fill in the value of array
    for(int i=0; i<n; i++){
        cout << "fill in the "<< i+1 << " number. :";
        cin >> array[i];
    }

    sort(array, n);
    return 0;
}
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
void mean(int new_array[], int num){
 //GET TOTAL & CALCULATE MEAN
    float total;
    for(int i=0;i<num; i++){
        total += new_array[i];
    }
    cout << "The mean is " << total/num << endl;
    mode(new_array, num);
    }
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
void median(int new_array[], int num){
    //CALCULATE THE MEDIAN (middle number)
    if(num % 2 != 0){// is the # of elements odd?
        int temp = ((num+1)/2)-1;
        cout << "The median is " << new_array[temp] << endl;
    }
    else{// then it's even! :)
        cout << "The median is "<< new_array[(num/2)-1] << " and " << new_array[num/2] << endl;
    }
    mean(new_array, num);
}
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
void mode(int new_array[], int num) {
    int* ipRepetition = new int[num];
    // alocate a new array in memory of the same size (round about way of defining number of elements by a variable)
    for (int i = 0; i < num; i++) {
        ipRepetition[i] = 0;//initialize each element to 0
        int j = 0;//
        while ((j < i) && (new_array[i] != new_array[j])) {
            if (new_array[i] != new_array[j]) {
                j++;
            }
        }
        (ipRepetition[j])++;
    }
    int iMaxRepeat = 0;
    for (int i = 1; i < num; i++) {
        if (ipRepetition[i] > ipRepetition[iMaxRepeat]) {
            iMaxRepeat = i;
        }
    }
    cout<< "The mode is " << new_array[iMaxRepeat] << endl;

}
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////

void sort(int new_array[], int num){
     //ARRANGE VALUES
    for(int x=0; x<num; x++){
         for(int y=0; y<num-1; y++){
             if(new_array[y]>new_array[y+1]){
                 int temp = new_array[y+1];
                 new_array[y+1] = new_array[y];
                 new_array[y] = temp;
             }
         }
     }
    cout << "List: ";
    for(int i =0; i<num; i++){
        cout << new_array[i] << " ";
    }
    cout << "\n";
    median(new_array, num);
}
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////////

Answer 1

Don't forget to initialise your variables:

float total = 0.0f;

In C++, a variable with automatic storage duration can be left uninitialized. Using such a variable will give you undefined behaviour.

Answer 2

For one thing, you haven't initialized some of your variables. In mean(), for instance, you should have this:

float total = 0;

Variables are not initialized to any defined value by default.

I recommend you increase the warning level on your compiler. If you're using g++, use -Wall. That would detect problems such as using uninitialized variables and unused variables (which you have in main()).

Answer 3

Mode is one of the basic statistical operators; it represent the element with the highest frequency in an array.

Your function mode is a implementation of this operator: it creates a new array in which it stores the frequency of each element in the array(i.e. how many times each element appears). The function returns the element with the highest frequency or, in case there are more with the same highest frequency, it returns the larges one.

Hope it helps