Need to figure out what is going wrong with my source code. When I imput the values of 72, 69, and 2.8 respectively I should output pdf=0.85801, however I am not getting that value. I don't know why. I am doing the adaptive simpsons method to find the probability density of data under a normal curve. I believe that I might have the "approx" in the wrong spot, or I'm not calling my functions correctly. This like will take you to a PDF of what I am trying to do, I'm totally lost at this point.
#include<stdio.h>
#include<stdlib.h>
#include<math.h>
double INV_SQRT_2PI= 0.39894228; /*1/sqrt(2*pi)*/
double a, b, u, U, O, c, left, right, d, approx, x;
double epsilon= 0.0000001; /*epsilon defined as 0.0000001*/
double f(double x); /*prototype functions*/
double S(double a, double b);
double asimpson(double a, double b, double approx, double epsilon);
int main(void)
{
printf("Enter x Value: ");
scanf("%lf", &x);
printf("Enter Mean: ");
scanf("%lf", &U);
printf("Enter Standard Deviation: ");
scanf("%lf", &O);
double pdf, u;
u=((x-U)/O);
pdf=((1/2)+INV_SQRT_2PI * asimpson(0,u,S(0,u),epsilon));
printf("pdf= %f",pdf);
return 0;
}
double f(double x)
{
return (exp(double(x*x*(-1))/2));
}
double S(double a,double b)
{
return ((b-a)/6)*(f(a)+(4*f((a+b)/2))+f(b));
}
double asimpson(double a,double b,double approx, double epsilon)
{
approx= S(a,b);
c=((a+b)/2);
left=S(a,c);
right=S(c,b);
d=((left+right-approx)/15);
if(abs(d)<=epsilon)
return (left+right+d);
return (asimpson(a,c,left,epsilon/2)+asimpson(c,b,right,epsilon/2));
}
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