How to construct cubic splines?

Question

Momo 2018-2-24

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https://ww2.mathworks.cn/matlabcentral/answers/384619-how-to-construct-cubic-splines

编辑： Momo 2018-2-27

Hello, I am trying to implement the following code in Matlab but it dose not work.

x = 2*pi*[0 1 .1:.2:.9];
y = cos(x);
csp = csape( x, y, 'periodic' );
hold on
fnplt(csp,'g')
hold off

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Answer 1

John D'Errico 2018-2-24

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https://ww2.mathworks.cn/matlabcentral/answers/384619-how-to-construct-cubic-splines#answer_306917

编辑：John D'Errico 2018-2-24

在 MATLAB Online 中打开

Do you have the curve fitting toolbox? CSAPE is part of that TB. (It used to be in the splines TB but that got merged into the curve fitting TB some years ago.)

My SLM toolbox (found on the file exchange) does allow periodic boundary conditions.

x = 2*pi*[0:.1:1];
y = cos(x);
SLM = slmengine(x,y,'knots',x,'endcond','periodic','regul',0,'result','pp','plot','on');

So a purely interpolating cubic spline, with periodic boundary conditions.

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John D'Errico 2018-2-24

编辑：John D'Errico 2018-2-24

在 MATLAB Online 中打开

At the command line, use the ver command. If you have that TB, you will see it listed. So, for me, I see this:

ver
...
Curve Fitting Toolbox               Version 3.5.6       (R2017b)

John D'Errico 2018-2-25

在 MATLAB Online 中打开

Works fine for me. Don't you hate that? ;-)

x = 2*pi*[0 1 .1:.2:.9];
y = cos(x);
csp = csape( x, y, 'periodic' );
fnplt(csp,'g')

Your release is only slightly older than mine, which should not be a problem.

Perhaps you have hurt the feelings of your computer recently? Try giving it flowers? My computer can hold a grudge. Ok. Only kidding.

Seriously, can you use the other tools from the curve fitting toolbox? If not, then you might have an installation problem with that toolbox. I'd check to see if there were corruption problems on your disk. Maybe try re-installing MATLAB from online - that is pretty quick with a fast connection.

I just looked at the release notes, but do not see any recent changes to csape.

Is the CFT in your search path? So while you have a license, perhaps your search path got screwed up?

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