### Numerical Integration

Numerical integration is the approximate computation of an integral using numerical techniques.

/**# Script Name: test.java

# Script Version:

# Date: 2005-3-15

# Author: Ben@fadshop.net

# Description: Calculate Numerical Integration of a function.

# @author ben

*/

/**

* @author ben

*/

public class test {

public static double func(double x) {

return Math.exp(x*x); //e^(x^2)

}

public static void main(String[] args) {

double start, end;

double x, y, total;

double step;

double temp;

start = 0; end = 3;

total = 0;

if (start > end) { // make sure start 〈= end

temp = start;

start = end;

end = temp;

}

step = (end-start)/100.0; // if step == 0 then infinite loop.

for(x = start+step/2; x 〈 end; x+=step){y = func(x); total += Math.abs(y)*step;

}

System.out.println("Total=" + total);

}

}

上面是用来计算定积分的函数。例子中的e

^{x2}是不能算出积分的,所以只能用这种方法蛮解. 用来计算0-3的定积分，误差小于1%(跟MATLAB比较)

## 2 Comments:

this is too slow.

Are you bored because xys.org is down? :)

It's not slow. Actually you can adjust the "step" to make sure you get satisfied result as you want. Yes, it's a compromise.

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