interp1 problem

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Hannah
Hannah on 7 May 2011
Hi, I am trying to use the interp1 function. I keep getting a NaN response. This is what I have tried:
EDU>> rho=[1.4133,1.3587,1.2614,1.1769,1.1032];
EDU>> T=[250,260,280,300,320];
EDU>> interp1(rho,T,275)
ans =
NaN
It is very simple, but I am trying to work my way up. Thank you

Answers (1)

Teja Muppirala
Teja Muppirala on 7 May 2011
Are you trying to find the value of rho given that T=275?
rho=[1.4133,1.3587,1.2614,1.1769,1.1032];
T=[250,260,280,300,320];
interp1(T,rho,275)
  2 Comments
Teja Muppirala
Teja Muppirala on 7 May 2011
Then you can do:
Ti = 275:320;
rho_i = interp1(T,rho,Ti)
You basically had your rho and T backwards.
Your code:
interp1(rho,T,275)
computes "When rho is 275, what is T?"
You get a NaN because 275 is way outside the data for rho, and by default it does not extrapolate outside the original data range.

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