Evaluating polynomial at a certain x point to find y?

Hi all, so I have a script that evaluates the 1st through 4th degree polynomials of a given dataset of volume of liquid vs vol. of ice. I already did everything and plotted it just fine, the only thing I want to do is evaluate it for when x = 1.5 (vol. of liquid) for the 4th degree polynomial.

The script: https://pastebin.com/tcuM5bBk

What I wanted/tried to do is just evaluate the anonymous function, but it's within the for-loop and I don't know to pull the 4th iteration so I can evaluate it at 1.5. Any tips?

Answer 1

[KSSV]

As you have (x,y) data in hand....you can use interpolation. Read about interp1.

iwant = interp1(x,y,1.5) ;

Answer 2

[Torsten]

coeff{i} = polyfit(volHotLiq, volIce, i);
if i==4 
  p_15 = polyval(coeff{i},1.5);
end

Answer 3

[Emanuele Joy]

You're golden. I keep forgetting when to use the interp1 function. Thank you so much!