Thread: Issue with Random Number Generation

What would you consider a "sensible answer" for w?

Originally Posted by sam.briggs

Hey everyone,

Having some problems with generating a random number w. I'm using an algorithm to create w by generating two numbers between -1 and 1 and then squaring them and then summing then and then using user in putted means and standard deviations to generate tailor made distributions of random numbers. Here it is: NO code please just advice on what I'm doing wrong as if you run it it never produces sensible answers for w:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main()
{
    double x, y, z, m, s, w;                                                            //Define set of doubles for data storgae
    int i, N;                                                                              //Define Integer for counting purposes

printf("Please input the standard deviation you require:");                              //Acquire sigma data
scanf("%f",&s);
printf("\nPlease input the mean value you require from the Gaussian distribution:");    //Acquire mu data
scanf("%f",&m);
printf("\nPlease state the number of random variables you would like printed:");
scanf("%d",&N);

    for(i=0; i<N; i++)                                                                 //Generate random variable z between 0 and 1
    {
        x = 2* rand()/(double)RAND_MAX -1.0;
        y = 2* rand()/(double)RAND_MAX -1.0;
        z = (x*x) + (y*y);

        if(z<1)
        {
            w = ((s*x*sqrt((-2.0*log(z))/(double)z))+m);
            printf("x=%f, y=%f, z=%f, w=%f\n",x,y,z,w);
        }
        else
        {
            printf("Z is invalid=%f, x=%f, y=%f\n",z,x,y);
        }
    }

return 0;
}

Thanks once again guys! XD

The '%f' format specifier in scanf expects the address of a float, not a double. Fix that first and then come back if it still doesn't work as expected.

Cheers guys that sorted it out! XD