determine a relationship from Curve fitting

Well i am learning about curve fitting but got confused about one question and could not find proper help elsewhere. How do i find the relationship of a particular form in the curve fitting. I have the date given below: T= 200 600 1000 1400 K= 1.0 0.4 0.3 0.25

so i plot the given data using: %%Given data T=[200 600 1000 1400];% temperature K=[1 0.4 0.3 0.25];%thermal conductivity plot(T,K,'*')%ploting the data

now how do i determine a relationship of a specific form Tk^a=b with the given data.suppose a and b are constants.

Answer 1

[Star Strider]

A little algebra gives K=(b/T)^(1/a).

Using nlinfit:

T=[200 600 1000 1400];
K=[1 0.4 0.3 0.25];
Kfit  = @(B,T) (B(2)./T).^(1./B(1));                        % Model
B = nlinfit(T, K, Kfit, rand(2,1));
Tv = linspace(min(T), max(T));

figure(1)
plot(T,K,'*')
hold on
plot(Tv, Kfit(B,Tv), '-r')
hold off
grid

giving a=1.3 and b=199.

[S.Sil]

thanks.. how do i get the answers a and b as its not showing in my case.

[Star Strider]

My pleasure.

The easiest way is to just remove the semicolon (;) from the end of the nlinfit call:

B = nlinfit(T, K, Kfit, rand(2,1))

with a=B(1) and b=B(2).