How can I fit data using quartic smoothing splines?

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Thomas Erdosi
Thomas Erdosi 2012-7-25
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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Thomas Erdosi
Thomas Erdosi 2012-7-28
I need to exactly replicate the results of a paper that uses quartic

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回答（2 个）

Isabella Osetinsky-Tzidaki
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 );
Azzi Abdelmalek
Azzi Abdelmalek 2012-7-28
%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
  2 个评论
Thomas Erdosi
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
Thomas Erdosi 2012-7-30
Isn't there anyone who can help..? This must be possible to do in MATLAB.

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