Curve Fitting Tool Equation Issue

Hi to everybody,

my name is Leo and I am 26. I have an issue regarding the Curve Fitting Toolbox. I have three historical time series, I have performed the fitting and now I have my poly4 normalized curve that approximates to raw input data. My question is: how can I get Fitted Curve Values? I have tried to denormalize data then substitute it to the equation I got but I obtain something like the original time series and not the fitted curve. Any suggestion?

Thank you very much in advance to everyone!

Leo

This is the code I have used to try to get the curve:

%%Denormalizer

% Start...

p1 = .2442;
p2 = -.1398;
p3 = -.2358;
p4 = -2.233;
p5 = 24.05;

for x = SP99(1:252,1)

      y = (x - 1327)/57.19;
      Curve = p1*y.^4 + p2*y.^3 + p3*y.^2 + p4*y + p5;

end

And this is the curve of I want to obtain values:

Answer 1

[Star Strider]

I don‘t have the Curve Fitting Toolbox, but if you have all the fitted parameters and you want to get the values for the curve, one way is to use an anonymous function:

p(1) = .2442;
p(2) = -.1398;
p(3) = -.2358;
p(4) = -2.233;
p(5) = 24.05;

      y = (x - 1327)/57.19;
      Curve = @(y,p) p(1)*y.^4 + p(2)*y.^3 + p(3)*y.^2 + p(4)*y + p(5);

Then to get the values of Curve for every value of y:

yfit = Curve(y,p)

[Leonardo Urbano]

Thank you for your answer!

I have tried but I get the same result I described before:

[Leonardo Urbano]

Sorry, you're right! In the end we got the same (correct) result with two different ways! Comparing the two curves we get they differs only by the scale, but values are the same!

Matter solved :)

Thank you very much!

[Star Strider]

If you want to plot the equation for the fitted curve, plot it this way:

plot(y, yfit)

It looks like you‘re simply plotting your original data in the plot you posted in your comment.

[Image Analyst]

Leonardo, attach your code to get SP99, and data file with the paper clip icon.