MATLAB: How to know the new value of y after spline interpolation

interpolationspline

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?

Best Answer

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.
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