How to obtain R square value

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Hi all,
coefficientsold = polyfit(AAT,QErot1,1)
Ygg=polyval(coefficientsold,AAT)
figure
axis([-10 80 0 15])
plot(AAT,QErot1,'s',AAT,Ygg,'--','MarkerFaceColor',[0 0 0])
By using this code what I obtain is a linear equation that fits my data, but I am not able to obtain the R-square value.
I would be glad if you could tell be how to obtain the r-square value, if it is possible by the use of the regress function, because I am not able to understand the use of this function properly.
Thank you very much
Andoni

Accepted Answer

Star Strider
Star Strider on 1 Sep 2014
Use the core MATLAB corrcoef function. It will give you the R values and the significance levels (probabilities) and confidence intervals if you want them.
  6 Comments
Andoni Mendialdua
Andoni Mendialdua on 1 Sep 2014
Thank you, and what about the R matrix? what does 0.938 value mean?
Andoni
Star Strider
Star Strider on 1 Sep 2014
My pleasure!
The 0.938 value is the correlation coefficient for your data. I refer you to the documentation (hyperlink in my original Answer) for a full explanation. (The 1 values on the diagonal of the R matrix are because each variable is perfectly correlated with itself. This is correct, even though the corresponding P values equal to 1 on the diagonal of the P matrix are not correct.)

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More Answers (1)

Kalpesh Patil
Kalpesh Patil on 1 Sep 2014
correlation_coeff = corr2(Ygg,AAT);
r_sqr = power(correlation_coeff,2);
  4 Comments
Iain
Iain on 1 Sep 2014
Why do you think that an R-squared value of 1 is wrong?
Are you actually asking for an RMS?
Andoni Mendialdua
Andoni Mendialdua on 1 Sep 2014
r-square is wrong because with the new equation I obtain, the results are not the same as my initial datas. Thank you,
Andoni

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