How can I fit data using quartic smoothing splines?

Question

Thomas Erdosi 2012-7-25

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https://ww2.mathworks.cn/matlabcentral/answers/44532-how-can-i-fit-data-using-quartic-smoothing-splines

编辑： Isabella Osetinsky-Tzidaki 2016-12-26

Dear Community,

I am looking for something exactly like the existing function SPAPS, but for quartic splines. For some reason the only built-in options appear to be quadratic, cubic, and quintic. I have tried solutions with the FIT function but I am not getting anywhere. Please note it is important that I can set knots, specify the smoothing parameter p and retract the values of the resulting function.

Thank you very much for your help!

Thomas

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John D'Errico 2012-7-28

So use quintic. WTP?

Thomas Erdosi 2012-7-28

I need to exactly replicate the results of a paper that uses quartic

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Answer 1

Isabella Osetinsky-Tzidaki 2016-12-26

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https://ww2.mathworks.cn/matlabcentral/answers/44532-how-can-i-fit-data-using-quartic-smoothing-splines#answer_248497

编辑：Isabella Osetinsky-Tzidaki 2016-12-26

Quoted from https://www.mathworks.com/help/curvefit/examples/how-to-construct-splines.html

k = 5; % order 5, i.e., we are working with quartic splines

x = 2*pi*sort([0 1 rand(1,10)]);

y = cos(x);

sp = spapi( optknt(x,k), x, y );

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Answer 2

Azzi Abdelmalek 2012-7-28

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/44532-how-can-i-fit-data-using-quartic-smoothing-splines#answer_54788

在 MATLAB Online 中打开

%let us take this example:

method='smoothingspline'
t=[0:10];y=sin(t);  %your signal
yfit=fit(t',y',method)    %interpolation function yfit

%now choose your new time vector with 0.1 sample time

 ti=0:0.1:10;yi=yfit(ti)
 plot(t,y,'r')      %your original signal
 hold on, plot(ti,yi,'+b');   %your new signal

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Thomas Erdosi 2012-7-28

Thank you for your answer. I have tried the same before using the fit function with specifying 'smoothingspline' as method but unfortunately this is more of a general smoothing solution and not the exact quartic smoothing spline I need. I have tried a few thing with fitoptions as well but without success. Does anybody know how to do this for the quartic smoothing spline? Thanks again

Thomas Erdosi 2012-7-30