How can I know the new value of y after spline interpolation?

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Ezz El-din Abdullah 2017-2-1

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编辑： Stephen23 2017-2-2

I used csaps() and assigned it into cs which is a structure that holds breaks (x-interpolated values), coefficients, order, dim, etc. But not the new value of y.

So how can I get this vector?

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KSSV 2017-2-2

Post your full code..

Image Analyst 2017-2-2

spline_demo.m

I don't know what csaps() is. What toolbox is that in? List it in the Products section below. In the meantime, attached is my spline interpolation demo.

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Answer 1

Stephen23 2017-2-2

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编辑：Stephen23 2017-2-2

在 MATLAB Online 中打开

According to the csaps documentation (part of the Curve Fitting toolbox), you can either use fnval:

 pp = csaps(...)
 yy = fnval(pp,xx)

or call csaps itself with the new X values to get the new Y values:

yy = csaps(x,y,p,xx)

For example:

 >> pp = csaps(0:pi,sin(0:pi));
 >> yy = fnval(pp,0:0.5:pi)
 yy =
     0.082568      0.46933       0.7632      0.88597      0.81813      0.57192      0.22799

It is easy to navigate the MATLAB help: all spline functions are listed here, with lots of help showing how to use them:

https://www.mathworks.com/help/curvefit/splines.html

Instead of getting confused, learn to read MATLAB's help, and learn how to browse the contents on the LHS of the page: it is arranged very nicely by topic.