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Ankush_1341-Visitor
1-Visitor
November 4, 2019
Solved

Interpolations and extrapolation of matrix.

  • November 4, 2019
  • 3 replies
  • 4959 views

Hello,

Newly introduced to MathCAD Prime 6.0 here and I want to put the following image as a matrix. Then, write a program where, at any given roof angle, between 0-30, and 1) if solidity ratio is 0 or 1, then interpolate to get  corresponding Cp value. 2) if solidity ratio is between 0 and 1, then do bi-linear interpolation to get a corresponding Cp value. 3) if solidity ratio is greater than 1, then extrapolate to get a corresponding Cp value.

Capture.PNG

Would really appreciate some help on how I could go about this. Thank you!

 

*EDIT* I have now been able to convert this data as a matrix. I used another thread as an example to be able to extract the roof angle matrix, Solidity ratio = [0  1] and the Cp values matrix. After this I am stuck on how to program the conditions stated above. Please refer to the mdcx file attached. Also familiar with the linterp, and interp functions. But unsure on how to use them for my requirements. 

 

Best answer by Werner_E

I did not look at your sheet as it wasn't attached from the beginning.

Unfortunately you don't show in the sheet you attached how you used my function.

So my best guess is that you forgot to transpose y.

The row and column headers must both be (column)vectors.

B.PNG

3 replies

L
LucMeekes23-Emerald IV
23-Emerald IV
November 4, 2019

Look up interpolation functions such as linterp(), interp() and spline functions.

 

Success!
Luc

    A
    Ankush_1341-VisitorAuthor
    1-Visitor
    November 4, 2019

    Hello, thank you for replying. I took a look at those functions earlier and added a worksheet to my original post with an update on what I did. Did something which seemed to work out but again hit another road block. 

    W
    Werner_E25-Diamond I
    25-Diamond I
    November 4, 2019

    I guess the routine(s) I posted here

    https://community.ptc.com/t5/PTC-Mathcad/3d-surface-plot-from-excel-data/m-p/370013/highlight/true#M144823

    should help.

     

    A
    Ankush_1341-VisitorAuthor
    1-Visitor
    November 4, 2019

    Hi, I actually used your and another person's feedback to create my solution. But in the f(x,y) values, when I input the values in the function, such as f(11,0). Then I get an error saying "this value must be a vector". 

    W
    Werner_E25-Diamond IAnswer
    25-Diamond I
    November 4, 2019

    I did not look at your sheet as it wasn't attached from the beginning.

    Unfortunately you don't show in the sheet you attached how you used my function.

    So my best guess is that you forgot to transpose y.

    The row and column headers must both be (column)vectors.

    B.PNG

      L
      LucMeekes23-Emerald IV
      23-Emerald IV
      November 4, 2019

      The Cp() function below may be what you are looking for.

      LM_20191104_Interpolation.png

      Success!
      Luc

        A
        Ankush_1341-VisitorAuthor
        1-Visitor
        November 5, 2019

        Hello, thank you for your solution. It was just as helpful as the other person as it gave a better perspective in programming the solution. Really appreciate your feedback. 

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