While using fit function, how to make sure the generated fit is only of the range of data points ?

Question

VIGNESH BALAJI 2023-7-21

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1999098-while-using-fit-function-how-to-make-sure-the-generated-fit-is-only-of-the-range-of-data-points

评论： VIGNESH BALAJI 2023-7-21

ok.png

I have 6 datapoints and I generated a fit but the the fit exceeds the range of my datapoints. I have attached an image to show it.

I have also attached my code, please let me know what options to choose to make sure that my git is exactly of the range of my datapoints.

%% fitting a cateanry curve equation
l = 1.76;                                               % physical length of catenary curve
fun = @(c)  (- l/2 + c * sinh(x_bar/(2*c))); x0 = 0.15;
c = abs(fzero(fun,x0));                                 % computes value of parameter a (sag)
xx = xy0(1,:)                                           % from dataset
yy = xy0(2,:)
ft = fittype('a*cosh((x)./a)+b', 'problem','a')        % b is the coefficient used by fit and it optimises b
[f, gof]=fit(xx(:), yy(:),ft,'problem', c) 

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

Matt J 2023-7-21

编辑：Matt J 2023-7-21

I have attached an image to show it.

I for one don't understand what the image is supposed to show. The fit looks pretty good, and its plot covers the same range of x values as the data shown there.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Matt J 2023-7-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1999098-while-using-fit-function-how-to-make-sure-the-generated-fit-is-only-of-the-range-of-data-points#answer_1276788

在 MATLAB Online 中打开

A fit does not have an inherent "range". Once the fit is computed, you can plot it over any range of x values that you wish, e.g.,

xp=linspace(min(xx(:)) , max(xx(:)));
plot(xp,f(xp))

1 个评论
显示 -1更早的评论隐藏 -1更早的评论

VIGNESH BALAJI 2023-7-21

@Matt J Thank you for the comment

请先登录，再进行评论。

Answer 2

the cyclist 2023-7-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1999098-while-using-fit-function-how-to-make-sure-the-generated-fit-is-only-of-the-range-of-data-points#answer_1276798

If you only supply 6 data points to the fitting function, it will only use those points. MATLAB doesn't "know" to do anything else.

But, that function still exists for all other points besides what was used to fit it. So, MATLAB can still plot it elsewhere. If you prefer not to plot beyond the range of the fitted points, then you can use the xlim function to limit where you plot.