How to write a function to find a value from a table.

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me 2016-7-17

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评论： Star Strider 2016-7-18

I have a table that looks like this https://www.ohio.edu/mechanical/thermo/property_tables/air/air_Cp_Cv.html. I need to write a function with temperature as the input and the other three points of data as the output, but I am unsure of how to set up the code? How do I write a code that also interpolates if the temperature value is between two points of known data? I am very very new to matlab and am not at all sure how to even start. Any help would be greatly appreciated. Thank you in advance!

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Image Analyst 2016-7-17

Is it a table, or a matrix of doubles? They're different and handled differently (look up table in the help if you don't understand why). Make it easy for us to help you by giving us code to generate the table variable, or matrix of doubles.

me 2016-7-18

it is the exact table on that site. I guess you could make a matrix of them instead. It doesn't matter which way it is done... the simplest way would be fine. essentially i would like to create a function for which i would input a Temperature and get the three specific heat values(Cp, Cv, and k). the code i have so far is not really relevant to the function...its where i plan to use the function to get those values. I am just not even sure how to do the function at all. As i said, I have very little experience with matlab.

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Answer 1

Star Strider 2016-7-17

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I would use the interp1 function.

You can easily make a function from it:

M = [ 250 1.003 0.716 1.401
      300 1.005 0.718 1.400
      350 1.008 0.721 1.398
      400 1.013 0.726 1.395];
CpCvk = @(TK) interp1(M(:,1), M(:,2:4), TK, 'linear', 'extrap');
T325 = CpCvk(325)
T325 =
       1.0065       0.7195        1.399