there is something i don't understand in the curve fitting tool box, i have :
x= [1 2 3 4];
y= [1 2 3 4];
after using the curve fitting tool box this is the results comes out:
Linear model Poly1:
f(x) = p1*x + p2
where x is normalized by mean 3.5 and std 1.871 Coefficients (with 95% confidence bounds): p1 = 1.871 (1.871, 1.871) p2 = 3.5 (3.5, 3.5)
Goodness of fit:
Adjusted R-square: 1 RMSE: 8.382e-16
the plotted graph on the right is correct but the resulted equation is not correct !!!!! ??
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Of course the equation is right--as the message says p1 and p2 are coefficients for the normalized x. Substitute in z=(x-3.5)/1.871 and solve for m and b in terms of z and you'll find that
m=p1/1.871 --> 1 b=p2+3.5 --> 0
In the tool it's the "Center and Scale" checkbox that controls it; at the command line the fit option 'Normalize', 'on|off'