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JP_105537373-Newcomer
3-Newcomer
February 10, 2023
Solved

Conditional Matrix Interpolation

Hello,

 

I'm trying to put this table in MathCAD:

JP_10553737_0-1676058457108.png

The goal is to have a function that will let me input just ADT and Design Speed, and then give me Runout Length. What is the best way to do this?

 

Thanks

 

Werner_E
Werner_EAnswer
25-Diamond I
February 11, 2023

Would it be a problem if the last column would be valid for ADT up to and including  1000 and the second last column for ADT greater than 1000 ? The difference is only the result if ADT is exactly 1000. Your table says that the third column  is to be used and I suggest using the fourth.
It makes the implementation a bit easier because for the other columns in your table its also valid that the upper limit is included and the lower is not (e.g. the second column includes 10000 but does not include 5000).

 

What about a Design Speed of 75 mph? Should the data be interpolated or should an error as of an invalid speed been thrown out?

 

I guess you don't want to interpolate the ADT value as otherwise we would need the "center" values for them - especially for the outer two columns..

 

Here is one possible way to do it in Mathcad:

Werner_E_0-1676080996584.png

 

Mathcad 15 worksheet attached (and also the file converted to Prime as I fear that you are not using Mathcad but rather Prime (also called Mathcad Prime))

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4 replies

ttokoro
ttokoro21-Topaz I
21-Topaz I
February 11, 2023

First step is

image.pngimage.pngimage.png

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t.t.
    Werner_E
    Werner_E25-Diamond IAnswer
    25-Diamond I
    February 11, 2023

    Would it be a problem if the last column would be valid for ADT up to and including  1000 and the second last column for ADT greater than 1000 ? The difference is only the result if ADT is exactly 1000. Your table says that the third column  is to be used and I suggest using the fourth.
    It makes the implementation a bit easier because for the other columns in your table its also valid that the upper limit is included and the lower is not (e.g. the second column includes 10000 but does not include 5000).

     

    What about a Design Speed of 75 mph? Should the data be interpolated or should an error as of an invalid speed been thrown out?

     

    I guess you don't want to interpolate the ADT value as otherwise we would need the "center" values for them - especially for the outer two columns..

     

    Here is one possible way to do it in Mathcad:

    Werner_E_0-1676080996584.png

     

    Mathcad 15 worksheet attached (and also the file converted to Prime as I fear that you are not using Mathcad but rather Prime (also called Mathcad Prime))

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      JP_105537373-NewcomerAuthor
      3-Newcomer
      February 13, 2023

      Thanks! I am using MathCAD Prime, and was hoping to be able to interpolate between design speeds. Your second solution is exactly what I was looking for.

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      DJF16-Pearl
      16-Pearl
      February 13, 2023

      Just another take on it, because the Heaviside function doesn't get enough love.  This doesn't interpolate EXCEPT at the exact matching ADT points (e.g. 1000) - when it averages the two.  If you used GEstep in excel you could avoid that.

      2023-02-13_15-44-23.png

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