How can I fit a curve at the bottom of the plot below?

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Stephen Tete 2023-7-4

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https://ww2.mathworks.cn/matlabcentral/answers/1991593-how-can-i-fit-a-curve-at-the-bottom-of-the-plot-below

编辑： Stephen Tete 2023-7-4

data.txt

I have the attached dataset and I want to fit a curve at the bottom of the curve. See the attached photo. The original data is in blue and the fit is that in black.

Sample data is attached. Thank you in advance

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采纳的回答

Matt J 2023-7-4

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1991593-how-can-i-fit-a-curve-at-the-bottom-of-the-plot-below#answer_1266848

编辑：Matt J 2023-7-4

在 MATLAB Online 中打开

data.txt

You can use boundary,

y=readmatrix('data.txt');

x=(1:numel(y))';

k=boundary(x([1:end,1]), y([1:end,1]));

k=k(diff(k)>0);

plot(x,y, x(k),y(k))

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Matt J 2023-7-4

在 MATLAB Online 中打开

y.txt

Ok, but what help do you still require? As you can see below, the recommendations from my last comment work for y.txt as well.

[~,y]=readvars('y.txt');

x=(1:numel(y))';

S=[1,0.7,0];

for s=S

k=boundary(x([1:end,1]), y([1:end,1]),s);

k=k(diff(k)>0);

plot(x(k),y(k),'-.');hold on

end;

legend("s="+S); xlim([100,400])

Stephen Tete 2023-7-4

编辑：Stephen Tete 2023-7-4

works great when s=0, Thank you very much

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