To caculate the Integrate by C Language

Discussion in 'C' started by wdliming, Jan 1, 2011.

1. wdlimingNew Member

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To caculate the Integrate by C Language
Code:
/*
*To achieve a particular function,To integrate f(x) = x; which is rom low to up
*sum=( (up-low)/n)*(f(x0)+f(x1)+...+f(x(n-1)) )
or sum=( (up-low)/n)*(f(x1)+f(x2)+...+f(x(n)) )
*Date:			2010-11-28
*modification:	2010-12-31 usage modification : else -> switch
*Version:		0.1.6
*Author:		wdliming
*description:	Using modular programming method
*/
#include <stdio.h>
#include <math.h>

double Integrate(double low,double up,	unsigned long int n,int F_Ch);
//double Func_Chioce(double x, int F_Ch);
void Start();

void Start()
{
printf("				Mini Integrate\n");
printf("				   LiMing\n");
printf("				version 0.1.5\n");
printf("Funcion 1:	f(x)=x;\n");
printf("Funcion 2:	f(x)=x*x;\n");
printf("Funcion 3:	f(x)=exp(x);\n\n");
printf("Please input a number to select a funcion to integrate:\n");
}

double Integrate(double low,double up, unsigned long int N,int F_Ch)
{
double temp=0;
double sum=0;
double temp_1=0;
if( ((low>-100)&&(low<100)) && ( (up>-100)&&(up<100)) && (low != up) )
{
/*First,low and up is between -100 and 100;Second,low != up;Third,up>low*/
printf("low=%lf,up=%lf.\n",low,up);

if( (N>0)&&(N<429467295) )
{
printf("N=%ld\n",N);
temp=(up-low)/N;
printf("temp=(up-low)/N=%lf\n",temp);
unsigned long int i;//counter i;
switch(F_Ch)
{
case 1:
for(i=1;i<=N;i++)
{
temp_1=low+temp*i;
sum = sum + temp_1;//This statement is very important!
}sum *= temp;
break;

case 2:
for(i=1;i<=N;i++)
{
temp_1=low+temp*i;
sum = sum + pow(temp_1,2);//This statement is very important!
}sum *= temp;
break;

case 3:
for(i=1;i<=N;i++)
{
temp_1=low+temp*i;
sum = sum + exp(temp_1);//This statement is very important!
}sum *= temp;
break;
}
/*if(F_Ch==1)
{
for(i=1;i<=N;i++)
{
temp_1=low+temp*i;
sum = sum + temp_1;//This statement is very important!
}
sum *= temp;
}
else if(F_Ch==2)
{
for(i=1;i<=N;i++)
{
temp_1=low+temp*i;
sum = sum + pow(temp_1,2);//This statement is very important!
}
sum *= temp;
}
else if(F_Ch==3)
{
for(i=1;i<=N;i++)
{
temp_1=low+temp*i;
sum = sum + exp(temp_1);//This statement is very important!
}
sum *= temp;
}*/
//printf("Successful!The result of integral is:%lf\n\n",sum);
}
else if(N<0)
{
printf("Failed!The number you input is illegal!\n");
printf("continue!\n");
}
else
{
printf("Failed!The number you input is too big!\n");
printf("continue!\n");
}
}
else
if( low == up )
{
printf("Successful!sum=%lf\n",sum=0);
printf("continue!Input the two Real Number a(low) and b(up) again: low,up.\n\n");
}
else
{
printf("Failed!The number(s) you input is(are) too big!\n");
printf("continue input the two Real Number a(low) and b(up) again: low,up.\n\n");
}
return sum;
}

int main()
{

double low=0;
double up=0;
double sum=0;
int F_Ch=0;
Start();
while(scanf("%d",&F_Ch))
{
if(F_Ch>0&&F_Ch<4)
{
printf("Selece Function %d;\n\n",F_Ch);

printf("Input the two Real Number a(low) and b(up) to \ndefine the area that you want to integral: low,up.\n");
printf("for example:0,2\n\n");

scanf("%lf,%lf",&low,&up);
printf("Input a number 'N':");
unsigned long int N;
scanf("%ld",&N);
sum=Integrate(low,up,N,F_Ch);
printf("Successful!The result of integral is:%lf\n\n",sum);
}
else
{
printf("error!\n");
}
}
return 0;
}
Welcome to give some constructive suggestions!Thank you!

Last edited by a moderator: Jan 2, 2011