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Excel (Solver) Query

  • 03-09-2010 2:51pm
    #1
    fed16
    Registered Users Posts: 53 ✭✭


    I need to find the root x of the following equation:

    A - (B/ln(C/x-D) - (K/ln(E/x-F)=0

    A, B, C, D, E, F & K are constants. So, while the equation has only one variable (x), I’ve not been able to figure out how to resolve it mathematically.

    However, it’s possible to resolve it iteratively in Excel, using the Excel solver.
    I need to repeat this iteration process for different constant values A,B,C,D,E,F & K. While Excel solver can resolve the equation, it can only be applied manually to an individual cell; I’ve not been able to find a way to apply the solver algorithm to a cell, and then copy & paste the solver routine across many cells.


Comments

  • #2
    JonathanAnon
    Closed Accounts Posts: 23,718 ✭✭✭✭JonathanAnon


    I'm not sure I fully understand which bit is not working for you, but is it possible to get the equation in terms of x = ******


  • #3
    Groinshot
    Registered Users, Registered Users 2 Posts: 1,042 ✭✭✭Groinshot


    If I were you, I'd be banging that into mathematica...


  • #4
    5uspect
    Moderators, Arts Moderators Posts: 10,518 Mod ✭✭✭✭5uspect


    The parenthesis on the equation aren't balanced.
    I presume you mean:

    [latex]A - \frac{B_1}{log(\frac{C_1}{x}-D_1)} - \frac{B_2}{log(\frac{C_2}{x}-D_2)}=0[/latex]

    where I've replaced constants E,F and K with B2 C2 and D2 for clarity.

    In Excel you would have to write a macro to run goal seek on each cell.
    You're probably better off solving the equation in Mathematica or Maple or even Matlab.


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