XMM-Newton Science Analysis System


ssclib (ssclib-4.36.3) [22.0.0-9173c7d25-20250127]

Trapezoid-rule, 1-D, numerical integral

Given two vectors $x$ and $y$ containing samples of a function $F$, this subroutine returns the `trapezoidal-rule' estimate of the integral of $F$. In other words, $F$ is replaced by the set of piecewise-continuous line segments defined by $x$ and $y$. Note that $x$ is assumed to be monotonically increasing - if it isn't, you'll get strange results.

  interface trapezoidSum
    function trapezoidSumSingle(x, y) result(summ)
      real(single), intent(in) :: x(:), y(size(x))
      real(single)             :: summ
    end function trapezoidSumSingle

    function trapezoidSumDouble(x, y) result(summ)
      real(double), intent(in) :: x(:), y(size(x))
      real(double)             :: summ
    end function trapezoidSumDouble
  end interface