Calculating average of specific lines in an array and storing in another array

Question

I'm trying to calculate the average of specific lines in an array. For example the format of the array looks like this:

float Array[20] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10,...20}

I want to calculate the average of the first 5 numbers in the array, then the average of the next 5 numbers and so on... storing them into another array with only the averages of those numbers.

Here's my code so far

float average_values[4];
for (int a = 0; a < 4; a++){    //20 elements in array divided by 5 = 4
    float sum = 0;
    for (int b = 0; b < (20 / 4); b++){
        sum = sum + scores[b];
    }
    average_values[i] = sum / (20 / 4);
}

Nick · Accepted Answer · 2017-03-12 17:48:39Z

1

#include <stdio.h>
int main()
{
        int scores[] = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11,12,13,14,15,16,17,18,19,20};
        float average_values[4];
        for (int a = 0; a < 4; a++)
        {    //20 elements in array divided by 5 = 4
            float sum = 0;
            for (int b = 0; b < (20 / 4); b++)
                sum = sum + scores[b+a*5]; // THIS IS THE BIT YOU'D MISSED
            average_values[a] = sum / (20 / 4);
        }
}

answered Mar 12, 2017 at 17:48

Nick

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Comments

P0W · Accepted Answer · 2017-03-12 17:37:23Z

0

Keeping aside all typos in your current post

I assume you have trouble in filling up your average_values array.

So assume scores array as matrix for 5 columns and 4 rows,

So your inner loop should look like:

for (int b = 0; b < 5; b++){
    sum = sum + scores[ a*5 + b];
                      //~~~ Correct index for next sets
}

answered Mar 12, 2017 at 17:37

P0W

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Comments

Jarod42 · Accepted Answer · 2017-03-12 17:43:32Z

0

With range-v3, it would be:

auto means = Array
             | ranges::view::chunk(5)
             | ranges::view::transform([](auto&& r) { return ranges::accumulate(r, 0.f) / 5; });

Demo

answered Mar 12, 2017 at 17:43

Jarod42

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