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prop_design15-Moonstone
15-Moonstone
December 14, 2021
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Some dumb questions about Classic Mathcad usage

  • December 14, 2021
  • 2 replies
  • 3650 views

hi,

 

I've forgotten how to work with data in classic mathcad. I have the questions in the file attached along with the data file. These are the three questions, for the sake of the post:

 

1) how to get x,y data into a function

2) how to assign units to the data

3) how to curve fit the data

 

The questions would apply to any x,y data set. This happens to be a fan pq curve.

 

Thanks,

 

Anthony

Best answer by Fred_Kohlhepp

you've already defined your units; to assign them to the variables, simply multiply  

Fred_Kohlhepp_0-1639500646312.png

Curve fitting is a whole 'nother art.  Shown is a seventh order polynomial

Fred_Kohlhepp_1-1639501348977.png

 

2 replies

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Fred_Kohlhepp23-Emerald IAnswer
23-Emerald I
December 14, 2021

you've already defined your units; to assign them to the variables, simply multiply  

Fred_Kohlhepp_0-1639500646312.png

Curve fitting is a whole 'nother art.  Shown is a seventh order polynomial

Fred_Kohlhepp_1-1639501348977.png

 

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    prop_design15-MoonstoneAuthor
    15-Moonstone
    December 14, 2021

    thanks fred,

     

    that reminded me on how to answer the first two questions. i ended up doing it in a spreadsheet though, since it was easier. i don't need to curve fit the data. i added that question in there because it seemed like a logical step people might be interested in.

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    prop_design15-MoonstoneAuthor
    15-Moonstone
    December 16, 2021

    i ended up having to do something similar to what i was trying to do before. this time it worked. not sure what i was doing wrong before. but attached was the basic issue. i had models from data and models from functions. i was trying to plot them in the same plot and couldn't. i ended up exporting the data and plotting it in a spreadsheet. this time, i could get the plot to work in mathcad. kinda weird.

     

    anyways, if this helps anyone, i attached the file. i wouldn't put too much weight into the math. that's a work in progress. the main thing is trying to plot two different mathcad data types. i was thinking i would have to convert the matrices into a function. but i guess that's not necessary.

     

    i'm still not sure how you could do that, even if you wanted to. right now the file has the matrices as is and the functions as is. there is no converting of either data.

     

    i should state this is a mathcad 15 file. same as my previous attachment.

     

    Edit; forgot to attach the data file

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    Werner_E25-Diamond I
    25-Diamond I
    December 16, 2021

    You could "convert the matrices into a function" by using either linear or spline interpolation, but as you wrote thats not necessary if you just want to plot the data.

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    prop_design15-MoonstoneAuthor
    15-Moonstone
    December 16, 2021

    ah, thanks werner

     

    the problem with curve fits of the data in a spreadsheet was it didn't get the last point right. you could force the first point to match but the last point would be off. i'm assuming mathcad would have the same issue.

     

    yesterday i had two formulas and one set of data. when i tried to plot it in mathcad it wasn't working. but i think it was my fault. not sure. but i think i got the hang of it now. i use mathcad so little that i completely forget how to use it. i was looking in the manual and couldn't find anything to help. sometimes it's hard to find the right thing in the manual, even though it's in there somewhere.

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