Skip navigation
1535 Views 9 Replies Latest reply: Feb 19, 2012 2:10 PM by A.Non RSS
ptc-4457992 Copper 5 posts since
Feb 12, 2012
Currently Being Moderated

Feb 12, 2012 11:05 PM

Explicit function definition

Hello,

 

I am quite new to Mathcad. What I want to do is to define a function explicitly (i.e., as pairs of x - y or x - f(x) values), not analitically (through a formula). Does anyone know wether that is possible or not? I am using Mathcad 14 and I searched the user guide, provided examples and tutorials, but couldn't find anything related to this subject. I even tried to do that myself, by improvising, but without any success.

 

Moreover, if it's possible to define a function explicitly, could one calculate definite integrals on it afterwards? (I know that is easy if the function is defined analitically).

 

Best regards,

Marius

  • MikeArmstrong Diamond 4,396 posts since
    Dec 3, 2008
    Currently Being Moderated
    Feb 12, 2012 11:40 PM (in response to ptc-4457992)
    Re: Explicit function definition

    Yes I believe it is possible, but I'm not sure exactly what your after.

     

    Could you provide an example and post the worksheet?

     

    Mike

  • VladimirN. Platinum 2,378 posts since
    Sep 26, 2010
    Currently Being Moderated
    Feb 12, 2012 11:42 PM (in response to ptc-4457992)
    Re: Explicit function definition

    Hello!

     

    Provide a screenshot of what you want.

  • FredKohlhepp Platinum 1,711 posts since
    Nov 28, 2006
    Currently Being Moderated
    Feb 13, 2012 3:46 AM (in response to ptc-4457992)
    Re: Explicit function definition

    Given an x,y data set there are several ways to proceed; the choice depends on the data and what you want to do.  With a dense and complete data set you can use numerical integration techniques.  You can curve fit the data--find a function that approximates the data closely, and use the built-in integration schemes for manipulation.

  • A.Non Diamond 10,324 posts since
    May 11, 2010
    Currently Being Moderated
    Feb 13, 2012 6:54 AM (in response to ptc-4457992)
    Re: Explicit function definition

    You need to create an interpolating function. The most general solution is a cubic spline, but it's not always appropriate. Without seeing the data it's hard to say much more.

      • A.Non Diamond 10,324 posts since
        May 11, 2010
        Currently Being Moderated
        Feb 19, 2012 2:10 PM (in response to ptc-4457992)
        Re: Explicit function definition

        We don't need the same reply four times. It's just as easy to read one reply four times as it is to read four replies

         

        I don’t need any curve fitting, interpolation function or any other kind of approximation.

        All numerical integration is approximate. The attached is a very general, and usually accurate, approach.

        Attachments:

More Like This

  • Retrieving data ...

Bookmarked By (0)

Legend

  • Correct Answers - 3 points
  • Helpful Answers - 1 points