Question

C++ ONLY!!! NOT JAVA.

The standard deviation is calculated from an array X size n with the equation

std=sqrt(sum((x_i-mean)²/(n-1)))

Sum the square of difference of each value with the mean. Divide that sum by n-1.

Take the square root and you have the standard deviation.

//System Libraries
#include <iostream> //Input/Output Library
#include <cstdlib> //Srand
#include <ctime> //Time to set random number seed
#include <cmath> //Math Library
#include <iomanip> //Format Library
using namespace std;

//User Libraries

//Global Constants, no Global Variables are allowed
//Math/Physics/Conversions/Higher Dimensions - i.e. PI, e, etc...
const float MAXRAND=pow(2,31)-1;

//Function Prototypes
void init(float [],int);//Initialize the array
void print(float [],int,int);//Print the array
float avgX(float [],int);//Calculate the Average
float stdX(float [],int);//Calculate the standard deviation

//Execution Begins Here!
int main(int argc, char** argv) {
//Set the random number seed
srand(static_cast<unsigned>(time(0)));
  
//Declare Variables
const int SIZE=20;
float test[SIZE];
  
//Initialize or input i.e. set variable values
init(test,SIZE);
  
//Display the outputs
print(test,SIZE,5);
cout<<"The average = "<<avgX(test,SIZE)<<endl;
cout<<"The standard deviation = "<<stdX(test,SIZE)<<endl;

//Exit stage right or left!
return 0;
}

Answer 1

Thanks for the question.

Here is the completed code for this problem. Let me know if you have any doubts or if you need anything to change.

Thank You !!
====================================================================================

//System Libraries
#include <iostream> //Input/Output Library
#include <cstdlib> //Srand
#include <ctime> //Time to set random number seed
#include <cmath> //Math Library
#include <iomanip> //Format Library
using namespace std;

//User Libraries

//Global Constants, no Global Variables are allowed
//Math/Physics/Conversions/Higher Dimensions - i.e. PI, e, etc...
const float MAXRAND=pow(2,31)-1;

//Function Prototypes
void init(float [],int);//Initialize the array
void print(float [],int,int);//Print the array
float avgX(float [],int);//Calculate the Average
float stdX(float [],int);//Calculate the standard deviation

void init(float arr [],int length){
   for(int i=0;i<length;i++){
       arr[i]=rand()/MAXRAND;
   }
}

void print(float arr [],int length, int columns){
       for(int i=0;i<length;i++){
       cout<<arr[i]<<" ";
       if((i+1)%columns==0){
           cout<<endl;
       }
   }
   cout<<endl;
  
}

float avgX(float arr [],int length){
   float total=0.0;
   for(int i=0;i<length;i++){
       total += arr[i];
   }
   return total/length;
}

float stdX(float arr [],int length) {
  
   float average = avgX(arr,length);
   double squareSum=0.0;
       for(int i=0;i<length;i++){
       squareSum += pow((arr[i]-average),2);
   }
   squareSum /=(length-1);
   return pow(squareSum,0.5);
  
}

//Execution Begins Here!
int main(int argc, char** argv) {
//Set the random number seed
srand(static_cast<unsigned>(time(0)));
  
//Declare Variables
const int SIZE=20;
float test[SIZE];
  
//Initialize or input i.e. set variable values
init(test,SIZE);
  
//Display the outputs
print(test,SIZE,5);
cout<<"The average = "<<avgX(test,SIZE)<<endl;
cout<<"The standard deviation = "<<stdX(test,SIZE)<<endl;

//Exit stage right or left!
return 0;
}

====================================================================================

thanks !