# Descriptive statistics

A bunch of basic statistical functions.
I could have made a class here and I could have used more features of C#. But just to keep it simple I left it as a console application. So the modifications you have to make if you're into C, C++, Java etc. should be minor.

``````using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Statistics
{
class Program
{
static void Main(string[] args)
{
Intro();
//////////////////////////////////////////////////////////
// TestAr could come from a file or userinput or whatever.
// Here TestAr is an array just for simplicity.
/////////////////////////////////////////////////////////
double[] TestAr = { 3.3, 5.77, 7.34, 9, 4.1, 13.66, 6.2, 7.65, 11.3, 12.67, 9, 10.03, 12.6, 3.76 };

Console.WriteLine("\tThe mean is  ............. : {0}", mean(TestAr.Length, TestAr));
Console.WriteLine("\tThe standard error is  ... : {0}", stderr(TestAr.Length, TestAr));
Console.WriteLine("\tThe median is ............ : {0}", median(TestAr.Length, TestAr));
Console.WriteLine("\tThe standard deviation is  : {0}", stddev(TestAr.Length, TestAr));
Console.WriteLine("\tThe variance is .......... : {0}", variance(TestAr.Length, TestAr));
Console.WriteLine("\tThe range is ............. : {0}", range(TestAr.Length, TestAr));
Console.WriteLine("\tThe minimum is ........... : {0}", min(TestAr.Length, TestAr));
Console.WriteLine("\tThe maximum is ........... : {0}", max(TestAr.Length, TestAr));
Console.WriteLine("\tThe sum is ............... : {0}", sum(TestAr.Length, TestAr));
Console.WriteLine("\tThe number of data is .... : {0}", TestAr.Length);
Console.WriteLine("");
Console.WriteLine("=========================================================");

}

static void Intro()
{
Console.WriteLine("=========================================================");
Console.WriteLine("|                                                       |");
Console.WriteLine("|                   Descriptive STATISTICS              |");
Console.WriteLine("|                                                       |");
Console.WriteLine("=========================================================");
Console.WriteLine("");
}

/// ==================================================================
/// Sums up all the numbers in an array arr with length len.
/// //////////////////////////////////////////////////////////////////
static double sum(int len, double[] arr)
{
double sum = 0.0;
for (int i = 0; i < len; i++)
{
sum += arr[i];
}
return sum;
}

/// ==================================================================
/// Calculates the MEAN of an array arr with length len.
/// The mean is given by sum of numbers/amount of numbers.
/// //////////////////////////////////////////////////////////////////
static double mean(int len, double[] arr)
{
return sum(len, arr) / len;
}

/// ==================================================================
/// Calculates the sample VARIANCE of an array arr with length len.
/// It is the sum of the squares of the difference of the numbers with
/// their mean, divided by the amount of numbers minus one.
/// //////////////////////////////////////////////////////////////////
static double variance(int len, double[] arr)
{
double m = mean(len, arr);
double sum = 0.0;
double d = 0.0;

for (int i = 0; i < len; i++)
{
d = arr[i] - m;
sum += d * d;
}
return sum / (len - 1);
}

/// ==================================================================
/// Calculates the STANDARD DEVIATION of an array arr with length len.
/// It is the square root of the variance
/// //////////////////////////////////////////////////////////////////
static double stddev(int len, double[] arr)
{
return Math.Sqrt(variance(len,arr));
}

/// ==================================================================
/// Calculates the STANDARD ERROR of an array arr with length len.
/// It is the standard deviation divided by the square root of the
/// amount of numbers.
/// //////////////////////////////////////////////////////////////////
static double stderr(int len, double[] arr)
{
return stddev(len, arr) / Math.Sqrt(len);
}

/// ==================================================================
/// Calculates the MINIMUM of an array arr with length len.
/// //////////////////////////////////////////////////////////////////
static double min(int len, double[] arr)
{
double mini = double.MaxValue;
for (int i = 0; i < len; i++)
{
if (arr[i] < mini)
{
mini = arr[i];
}
}
return mini;
}

/// ==================================================================
/// Calculates the MAXIMUM of an array arr with length len.
/// //////////////////////////////////////////////////////////////////
static double max(int len, double[] arr)
{
double maxi = double.MinValue;
for (int i = 0; i < len; i++)
{
if (arr[i] > maxi)
{
maxi = arr[i];
}
}
return maxi;
}

/// ==================================================================
/// Calculates the RANGE of an array arr with length len.
/// It is the difference between the largest and the smallest number.
/// //////////////////////////////////////////////////////////////////
static double range(int len, double[] arr)
{
return max(len, arr) - min(len, arr);
}

/// ==================================================================
/// Calculates the MEDIAN of an array arr with length len.
/// It is the middle value of an array of sorted numbers.
/// //////////////////////////////////////////////////////////////////
static double median(int len, double[] arr)
{
int i, j;
double temp;
for (i = 0; i < len - 1; i++)
{
for (j = i + 1; j < len; j++)
{
if (arr[j] < arr[i])
{
temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
}
}
if (len % 2 == 0)
return ((arr[len / 2] + arr[len / 2 - 1]) / 2.0);
else
return arr[len / 2];
}
}
}``````
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