Thursday, July 9, 2009

Average and standard deviation in c programming language?

i need a c program that calculates average of 10 number and standard deviation of those numbers. the program should include two functions, one for calculating average and the other for calculating standard deviation. number must be entered by user

Average and standard deviation in c programming language?
Here's a program I wrote a while back that does what you want.





#include %26lt;stdio.h%26gt;


#include %26lt;math.h%26gt;








int maxNums = 10; /*the max number of numbers we'll handle*/





/*function prototypes*/


double average(double nums[]);


double smplVar(double nums[]);


double stdDev(double nums[]);





int main()


{


printf("Enter the number of values:");


scanf("%d", %26amp;maxNums);





double numList[maxNums];


int i;








/* populate our array of numbers*/


for(i = 0; i %26lt; maxNums; i++)


{


scanf("%lf", %26amp;numList[i]);


}





/*handle our menu input*/


int choice = 0;


double answer;


while(1)


{


choice = printMenu();


if(choice == 1)


{


answer = average(numList);


printf("%f", answer);


}


if(choice == 2)


{


/*standard deviation is just the square root of the sample


*variation


*/


answer = stdDev(numList);


printf("%f", answer);


}


if(choice == 3)


{


answer = smplVar(numList);


printf("%f", answer);


}


if(choice == 4)


return 0;


}


}





/*print the menu and return the users choice*/


int printMenu()


{


printf("\n\nMenu:\n1)Average\n2)Standard Deviation");


printf("\n3)Sample Variance\n4)exit");


printf("\nPlease make a choice: ");





int choice;


scanf("%d", %26amp;choice);


return choice;


}





/*find and print the average*/


double average(double nums[])


{


double sum = 0;


int i;





/*add up all the numbers*/


for( i = 0; i %26lt; maxNums; i++)


sum += nums[i];





/*return the total/number of values (the mean)*/


return sum/maxNums;


}








/*finds the standard deviation


*=sqrt(sum)x-mean(x)^2)/n)


*/


double stdDev(double nums[])


{


double sum = 0;


double mean = average(nums);


int i;





for(i = 0; i %26lt; maxNums; i++)


sum += pow(nums[i]-mean, 2);





return sqrt(sum/maxNums);


}





/*finds the sample variance


*=(sum(x-mean(x)^2)/n)


*/


double smplVar(double nums[])


{


double sum = 0;


double mean = average(nums);


int i;





for(i = 0; i %26lt; maxNums; i++)


sum += pow(nums[i]-mean, 2);





return sum/(maxNums-1);


}


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