Let's consider

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taken from


Let's call the red points as : point 1, point 2, point 3, point 4.

I'm wondering if the spline part (the blue smooth line) between the point 1 and 2 would depend on the points number 3 and 4.

Said differently, does the spline between two points depend on other points that are outside the interval between these two points ?

  • 1
    $\begingroup$ Yes. With usual third degree splines, the spline coefficients are the solution of a tridiagonal system involving all interpolation points. $\endgroup$ Aug 25, 2021 at 11:49
  • $\begingroup$ @Jean-Claude Arbaut : thanks a lot $\endgroup$ Aug 25, 2021 at 11:50

1 Answer 1


For sure the spline in one interval depends on the previous and next interval for cubic splines. See this wikipedia article on the algorithm to compute cubic splines.

  • $\begingroup$ It doesn’t just depend on the points adjacent to the interval, it depends on all points. $\endgroup$
    – bubba
    Oct 24, 2021 at 8:08

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