Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Simpson method question(numerical analysis)

  1. Jun 25, 2010 #1
    i have been told that simpson with 3 points is a single panel



    a pannel is the distance between to points
    so if we have 3 points then we have 2 panels

  2. jcsd
  3. Jun 25, 2010 #2
    can't view the link clearly and what do you mean by pannel?
  4. Jun 25, 2010 #3


    User Avatar
    Science Advisor

    Simpson's method works by approximating a function by a "piecewise quadratic". If I understand your use of "panel" correctly, it is one of the quadratic pieces.

    Since a quadratic, [itex]y= ax^2+ bx+ c[/itex], has three coefficients to be determined, one quadratic, one panel, requires three points, not two, to determine those three coefficients.

    The "trapezoid method", where we approximate the function by a piecewise linear function, y= ax+ b, requires only two coefficients to be determined and so each "panel" requires two points.
  5. Jun 25, 2010 #4
    so how they use those three points in the formula
    i cant see where they use them on the arrow pointed formula
  6. Jun 25, 2010 #5


    Staff: Mentor

    In the last equation, the three points are (-1, f(-1)), (0, f(0)), and (1, f(1)).

    The equation could be rewritten as
    S1 = (1/3)[f(-1) + 4f(0) + f(1)].
  7. Jun 26, 2010 #6
    so a pannel is not an interval
    a panel in simpsons rule is 3 points (which has two intervals between them)
  8. Jun 26, 2010 #7
    thanks :)
  9. Jun 26, 2010 #8
    i tried to get to your expression by the formula
    if we have three points then we have 2 sub intervals

    you see that it requests 4 points
    and not
    x_0 x_1 x_2

    Last edited: Jun 26, 2010
  10. Jun 26, 2010 #9


    Staff: Mentor

    In Simpson's rule, you divide an interval [a, b] into n subintervals of equal length. In each subinterval you use function values evaluated at three points: the left endpoint, the middle, and the right endpoint.

    Instead of getting lost in the summation symbols, work out for yourself for some simple function and an interval [0, 1] divided into four subintervals. What does Simpson's rule give you for this situation?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook