C++ - Calculate Mean, Variance, Standard Deviation
Mean, Variance and Standard Deviation are widely used in statistical application. It is a good idea to start writing program in C++ on this.
Note the difference between sample variance and population variance, similarly sample standard deviation and population standard deviation
The complete program and test run output are given below:
Source Code
#include <iostream>
#include <string>
#include <math.h>
class StdDeviation
{
private:
int max;
double value[100];
double mean;
public:
double CalculateMean()
{
double sum = 0;
for(int i = 0; i < max; i++)
sum += value[i];
return (sum / max);
}
double CalculateVariane()
{
mean = CalculateMean();
double temp = 0;
for(int i = 0; i < max; i++)
{
temp += (value[i] - mean) * (value[i] - mean) ;
}
return temp / max;
}
double CalculateSampleVariane()
{
mean = CalculateMean();
double temp = 0;
for(int i = 0; i < max; i++)
{
temp += (value[i] - mean) * (value[i] - mean) ;
}
return temp / (max - 1);
}
int SetValues(double *p, int count)
{
if(count > 100)
return -1;
max = count;
for(int i = 0; i < count; i++)
value[i] = p[i];
return 0;
}
double GetStandardDeviation()
{
return sqrt(CalculateVariane());
}
double GetSampleStandardDeviation()
{
return sqrt(CalculateSampleVariane());
}
};
int main()
{
double arrNumbers[] =
{
15.17, 16.94, 14.94, 14.99, 13.77, 13.75,
12.67, 12.14, 12.59, 12.48, 14.81, 14.29,
12.74, 12.52, 11.65, 12.24, 11.42, 12.25,
12.72, 11.64, 11.09, 11.22, 11.50, 11.36,
11.84, 12.18, 11.04, 10.90, 11.80, 11.84,
};
StdDeviation sd;
sd.SetValues(arrNumbers, sizeof(arrNumbers) / sizeof(arrNumbers[0]));
double mean = sd.CalculateMean();
double variance = sd.CalculateVariane();
double samplevariance = sd.CalculateSampleVariane();
double sampledevi = sd.GetSampleStandardDeviation();
double devi = sd.GetStandardDeviation();
char buf[1024];
sprintf(buf, "Total Numbers\t\t\t: %10d\n", sizeof(arrNumbers) / sizeof(arrNumbers[0]));
std::cout << buf;
sprintf(buf, "Mean\t\t\t\t: %10.5lf\nPopulation Variance\t\t: %10.4lf\n", mean, variance);
std::cout << buf;
sprintf(buf, "Sample variance\t\t\t: %10.4lf\n", samplevariance);
std::cout << buf;
sprintf(buf, "Population Standard Deviation\t: %10.4lf\n", devi);
std::cout << buf;
sprintf(buf, "Sample Standard Deviation\t: %10.4lf\n", sampledevi);
std::cout << buf;
return 0;
}
Output
Total Numbers : 30
Mean : 12.68300
Population Variance : 2.1607
Sample variance : 2.2352
Population Standard Deviation : 1.4699
Sample Standard Deviation : 1.4951
Press any key to continue . . .
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