How can I fit data using quartic smoothing splines?
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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!
Isabella Osetinsky-Tzidaki on 26 Dec 2016
Edited: Isabella Osetinsky-Tzidaki on 26 Dec 2016
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 on 28 Jul 2012
%let us take this example:
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
plot(t,y,'r') %your original signal
hold on, plot(ti,yi,'+b'); %your new signal