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dsochor1-Visitor
1-Visitor
September 17, 2018
Solved

Create a function for line graph values?

  • September 17, 2018
  • 3 replies
  • 4446 views

In the attached Mathcad prime 3.1 worksheet (along with screenshot) I've graphed two vectors in an X-Y plot. Is it possible to create a function such that the user can type in any value for temperature( within the highest and lowest value) and receive the temperature back?

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Best answer by LucMeekes

Yes, that function is

 

GetTemp(Temp):=Temp

 

You call the function with, e.g.

GetTemp(15)=

and it results in

GetTemp(15)=15.

 

That's what you asked, but not what you meant to ask....

I'm afraid you want a function where you give an Ec value, and get the correcponding temperature. That is partially possible.

I think the answer to your question lies with the function linterp(), look it up in the help, and see how it works.

The problem is that there is a temperature range where the Ec value is 1. What temperature would you expect to get for Ec=1?

 

Success!
Luc

 

 

3 replies

L
LucMeekes23-Emerald IVAnswer
23-Emerald IV
September 17, 2018

Yes, that function is

 

GetTemp(Temp):=Temp

 

You call the function with, e.g.

GetTemp(15)=

and it results in

GetTemp(15)=15.

 

That's what you asked, but not what you meant to ask....

I'm afraid you want a function where you give an Ec value, and get the correcponding temperature. That is partially possible.

I think the answer to your question lies with the function linterp(), look it up in the help, and see how it works.

The problem is that there is a temperature range where the Ec value is 1. What temperature would you expect to get for Ec=1?

 

Success!
Luc

 

 

L
LucMeekes23-Emerald IV
23-Emerald IV
September 17, 2018

Here's an example using linterp().

LM_20180917_Linterp.png

Note that it works because there is a one-to-one relation between Temp and Ec values. If that is not the case (as in your example where Ec=1 on a range of Temp values), the linterp() funtion will complain. In that case using spline functions (see the answer below) may (...) help.

 

Success!

Luc

 

    R
    rgunwaldsen15-Moonstone
    15-Moonstone
    September 17, 2018

    Mathcad provides a variety of methods for fitting functions to data. 

     

    Attached worksheet fits cubic spline to your data.

      D
      dsochor1-VisitorAuthor
      1-Visitor
      September 17, 2018

      Thank you rgunwaldsen. What format (or version) is your worksheet; I'm unable to open it.

      R
      rgunwaldsen15-Moonstone
      15-Moonstone
      September 17, 2018

      I used Prime 5. PTC has made it impossible to copy/paste stuff into prior versions of Prime.

       

      Attached is "xps" printout.

       

      The functions used are straight out of the help example for "Example: Cubic Spline Interpolation

      Example: Cubic Spline Interpolation".
       
      Advantage for cubic spline fit for interpolation within range is that it provides "smooth" function with continuity of function and 1st/2nd derivatives.
       
      Roger
       
      W
      Werner_E25-Diamond I
      25-Diamond I
      September 17, 2018

      My guess is that you want a function to calculate Ec from a given temp and not the other way round.

      If linear interpolation is sufficient you may do like this:

      B2.png

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