My Code Feels A Little "Unpolished," Any Suggestions?

[RyanV]

Howdy guys,

I just had a project for my first year CompSci class where we had to design a
program that would generate a list of random numbers and then calculate their
standard deviation.

We haven't covered arrays yet, which meant we had to come up with a way to
calculate standard deviation without recording the values.

There were also the following predefined functions we were required to use:

void getParameters(int& seed, int& n, int& lower, int& upper);
// get the value for seed, number of random integers, lower and upper bound for those random integers.
int getNum(int lower, int upper);
// Generate a random integer between the lower and upper bound and return the integer.
void update(int num, double& sum1, double& sum2);
// update sum of values and sum of value squared
void output(double avg, double std);
//Output the two numbers. 

I'm not sure whether we could add functions or not, but I did.

Anyways, this is the code that I came up with. It works, although the
Standard Deviation it produces is usually .01 or so off from the "real"
STDEV.

However, the code feels a little, unpolished, to me. I feel I could have coded
it cleaner.

Does anyone have any suggestions on how I could have cleaned this up?

#include <iostream>
#include <cmath>
#include <cstdlib>

using namespace std;

void getParameters(int& seed, int& n, int& lower, int& upper);
// get the value for seed, number of random integers, lower and upper bound for those random integers.
int getNum(int lower, int upper);
// Generate a random integer between the lower and upper bound and return the integer.
void update(int num, double& sum1, double& sum2);
// update sum of values and sum of value squared
void output(double avg, double std);
//Output the two numbers.
int average(int n, int sum);
//Calculates the average of a sum of n integers
void average(int n, double sum1, double& avg);
//Calculates the average of the random values
void standardDeviation(double avg, int n, double sum1, double sum2, double& std);
//Calculates the standard deviation
void resetAll(double& avg, double& sum1,double& sum2, double& std, int& count, int& lower, int& upper, int& n, int& seed);
//Resets all variables so the program may be run again

int seed;

int main(){
    cout.setf(ios::fixed | ios::showpoint);
     cout.precision(2);
    int count = 0, lower, upper, n;
    double avg, sum1, sum2, std;
    char repeat = 'y';
    do {
        srand(seed);
        getParameters(seed, n, lower, upper);
        cout << "The numbers generated are: " << "\n";
        do {
            update(getNum(lower, upper), sum1, sum2);
            }
            while(++count < n);
            average(n, sum1, avg);
            standardDeviation(avg, n, sum1, sum2, std);
            output(avg, std);
            resetAll(avg, sum1, sum2, std, count, lower ,upper ,n, seed);
            cout << "\n" << "Would you like to continue? (y or n): ";
            cin >> repeat; }
        while(repeat == 'y' || repeat == 'Y');
}

void getParameters(int& seed, int& n, int& lower, int& upper) {
     cout << "\n" << "Seed for the random number generator: ";
     cin >> seed;
     cout << "\n" << "The size of the sequence: ";
     cin >> n;
     cout << "\n" << "Lower and upper bound for the random numers: ";
     cin >> lower;
     cout << " ";
     cin >> upper;}
     
int getNum(int lower, int upper){
    int value = ((rand() % (lower - upper + 1)) + lower);
    cout << value << " ";
    return value;  }
    
void update(int num, double& sum1, double& sum2) {
     sum1 = num + sum1;
     sum2 = (num * num) + sum2;  }

void average(int n, double sum1, double& avg) {
    avg = (sum1 / n);  }
    
void standardDeviation(double avg, int n, double sum1, double sum2, double& std) {
     std = sqrt((sum2 -(2*avg*sum1) + (n*avg*avg))/n); }
    
void output(double avg, double std) {
     cout << "\n" << "Average = " << avg 
          << " Standard deviation = " << std; }
          
void resetAll(double& avg, double& sum1,double& sum2, double& std, int& count, int& lower, int& upper, int& n, int& seed) {
     count = 0, lower = 0, upper = 0, n = 0;
     avg = 0, sum1 = 0, sum2 = 0, std = 0, seed = 0;}

[Disch]

Do you know about classes and structs? You could simplify/clean this up by making this a class instead of a series of global functions.

Other than that, the main thing I noticed was that you really like to pass by reference, which I usually try to avoid whenever possible. You should prefer to return variables when you can, as it's a lot more flexible.

That is..

// what you have:
void average(int n, double sum1, double& avg) {
    avg = (sum1 / n);  }

// what would be better:
double average(int n,double sum1) {
    return (sum1 / n);  }

EDIT:

I'm also not a fan of your indentation/brace style, but that's just a preference thing I guess.

[ne555]

It works, although the Standard Deviation it produces is usually .01 or so off from the "real" STDEV.

¿How are you calculating the "real" STDEV? It may be dividing by n-1 instead of n

You forgot to initialize some variables, and you are calling srand before obtain the seed.

[RyanV]

Do you know about classes and structs? You could simplify/clean this up by making this a class instead of a series of global functions.

Other than that, the main thing I noticed was that you really like to pass by reference, which I usually try to avoid whenever possible. You should prefer to return variables when you can, as it's a lot more flexible.

No, we haven't learned anything about classes and structs yet.

Most of the passing by reference was as a requirement for the assignment
since we just learned passing by reference, but you make a good point. Thank you.

How are you calculating the "real" STDEV? It may be dividing by n-1 instead of n

You forgot to initialize some variables, and you are calling srand before obtain the seed.

Lol, yeah, I realized I called srand too early about 5 minutes after I had emailed
the assignment to my TA :-D.

I'm not sure how the real STDEV was calculated, I found a site online where you put
numbers in and it gives you the avg and stdev, mine was just a hair off of theirs.

As far as initializing variables, I feel like a noob now, what do you mean by that?

Thanks.

[ne555]

double avg, sum1, sum2, std; //you should set sum1 and sum2 to 0
//...
update(getNum(lower, upper), sum1, sum2); //because they are used here as accumulators
//sum1 = num + sum1 

[mj1709]

well dunno wat seed is but the following program seems to be shorter and more efficiet for calculating the standard deviation for a set of random numbers...

#include<conio.h>
#include<math.h>
#include<stdlib.h>
main()
{
int k,i=1,n,l;
float s=0,m=0,stdev,mean;
clrscr();
//write a program that genrates 10 random numbers between 0-99 and prints the standard deviation of those numbers.....
randomize();
printf("enter the upper limit for the random function : ");
scanf("%d",&l);
printf("The size of the sequence : ");
scanf("%d",&n);
printf("The random numbers generated are : \n");
while(i<=n)
{k=random(l+1);
printf("%d\t",k);
m+=k;
s+=k*k;
i++;
}
mean=m/n;       //the keypoint here is the apporach or method u use to calculate standarddev
if((s-n*m*m)>0)
stdev=sqrt((s-n*m*m)/n);
else
stdev=sqrt((n*m*m-s)/n);
printf("average : %f\n",mean);
printf("standard deviation : %f\n",stdev);
getch();
}