How to enter the R-square fit formula in the m-file?

I need to calculate the R-square fit for the model output. I have the formula for calculating it, but how to give it in the code and what is the plot command to get the r-square fit?

Please do help me.

Answer 1

[Wayne King]

Residual sum of squares

residsumsq = norm(y-yhat,2)^2;

Total sum of squares

tsumsq = norm(y-mean(y),2)^2;

R2 = 1-(tsumsq/residsumsq);

[Priya]

Could anyone please tell how does this assigns the value for y, yhat from the plots and what should be the plot command to get the rsquared fit?

[Wayne King]

The y vector is the vector of your original data. The yhat vector is your fitted data as predicted by your model.

[Priya]

Please tell me what does the 2(in bold) in the below expression mean?

residsumsq = norm(y-yhat, 2 )^2;

Also, Is the norm function referring to summation?