trapzFunction function

double trapzFunction(double a, double b, int n, Function f,)

Compute the numerical integration of f() using the trapezoidal rule.

• a : start interval of the integration
• b : final interval of the integration
• n : number of the points between the interval
• f : function to integrate

References

1. "Numerical integration". https://rosettacode.org/wiki/Numerical_integration#Java. Retrieved 2019-07-31.

Examples

var i = trapzFunction(0, 2*pi, 20, (x) => cos(x));

print(truncate(i, 4));

/* output:
0
*/

Implementation

double trapzFunction(double a, double b, int n, Function f) {
  var range = checkParamsGetRange(a, b, n);
  var nFloat = n.toDouble();
  var sum = 0.0;
  for (var i = 1; i < n; i++) {
    var x = a + range * i.toDouble() / nFloat;
    sum += f(x);
  }
  sum += (f(a) + f(b)) / 2.0;
  return sum * range / nFloat;
}