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dsochor1-Visitor
1-Visitor
September 17, 2018
Solved

Create a function for line graph values?

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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LucMeekesAnswer
23-Emerald V
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

 

 

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6 replies

LucMeekes23-Emerald VAnswer
23-Emerald V
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

 

 

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LucMeekes23-Emerald V
23-Emerald V
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

 

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    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.

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      dsochor1-VisitorAuthor
      1-Visitor
      September 17, 2018

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

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      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
       
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      Werner_E
      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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