CODEWITHSUNDEEP
c++mathvectorpercentage
Yugenswitch
Yugenswitch

Reputation: 185

percentage calculation in my function is not working

so what I am trying to do is take a vector of numbers, find the number of time each element occurs then calculate the percentage equivalent of its number of occurances in the vector.

it works perfectly well on a vector with a few elements of only one number but not at all with a vector of different elements (2 to be exact) occuring multiple times.

here is a detailed output:

count = 6
pushed back 21
total = 6
percent = 6 / 6* 100
pushed back 100
Number:
21 
Percent Chance
100 

count = 5
pushed back 42
count = 5
pushed back 21
total = 5
total = 10
percent = 5 / 10* 100
pushed back 0
percent = 5 / 10* 100
pushed back 0
Number:
42 
Percent Chance
0 // SHOULD BE 50
Number:
21 
Percent Chance
0 // SHOULD BE 50

Here is the Code: (the output is from this function running twice with a different x vector)

 std::vector <std::string>  findpercentages(std::vector <std::string> x)
 {
 int count{};                          //for amount of times element occurs
 std::vector <std::string> tempvec{};  //to hold the element/s
 std::vector <int> counts{};           //to hold count for each element in tempvec
 std::vector <std::string> finalvec{}; //elements and counts of elements
 for (size_t i = 0; i < x.size(); i++)
 {
    //look for x[element] in tempvec, if not in tempvec, count occurances in x and add element to 
    // tempvec, add count to counts 
    std::vector <std::string>::iterator point { std::find(tempvec.begin(), tempvec.end(), x[i]) };
    if (point == tempvec.end())
    {
        count = std::count(x.begin(), x.end(), x[i]);
        std::cout << "count = " << count << '\n';
        counts.push_back(count);
        std::cout << "pushed back " << x[i] << '\n';
        tempvec.push_back(x[i]);

    }
}
int total{};
for (size_t n = 0; n < counts.size(); n++)
{
    total += counts[n]; //total for percentage calculation
    std::cout << "total = " << total << '\n';
}
for (size_t y = 0; y < tempvec.size(); y++)
{
    finalvec.push_back(tempvec[y]);
    //percent calculation. used unsigned_int64 because got arithmatic overflow warning if i just use 
    // int
    unsigned __int64 percentage = static_cast <unsigned __int64> (round((counts[y] / total) * 100));
    std::cout << "percent = " << counts[y] << " / " << total << "* 100" << '\n';
    finalvec.push_back(std::to_string(percentage));
    std::cout << "pushed back " << percentage << '\n';
}
return finalvec;
}

Upvotes: 0

Views: 418

Answers (1)

john
john

Reputation: 87944

unsigned __int64 percentage = static_cast <unsigned __int64> (round((counts[y] / total) * 100));

should be something like

double percentage = round((100.0 * counts[y]) / total);

Your problem is that when you divide one integer by another you always get a integer. So (counts[y] / total) is always going to be 0 or 1.

So the simplest solution is to introduce a double value 100.0 into the calculation. This makes sure that you get floating point division instead of integer division.

Upvotes: 2

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