Re: Interpolation on scattered data

[Nicklas Karlsson]

As there are several values for each point I where able to get a good triangulation of area by supplying other values for the same indexes. Maybe this is a good time implementing the missing function, it should not be to hard for linear interpolation.

Interpolation using delaunay triangulation is useful then working with data both from measured data and from solved partial differential equations, for example using the Finite Element Method.

Nicklas Karlsson

Den mån 23 mars 2020 kl 14:57 skrev Francesco Potortì <address@hidden>:

>linear, cubic, and natural methods are all triangulation based.  they take
>the scattered points, use octave's delauney triangulation, then calculate
>local interpolants within the triangles. linear (actually bilinear i guess)
>is simply a weighted some of triangle areas (the interpolation point
>creates three sub-triangles within the mesh triangle, and value is a
>weighted projection inversely proportional to sub-triangle size, where a
>big sub-triangle has you more strongly weighted toward the point not
>associated with that sub-triangle).  the v4 method does not triangulate,
>and does a weighted interpolation over the entire mesh. that can get slow
>and memory intensive, but it's currently the only 'smooth' interpolation
>function Octave has implemented (sort of).

Have you considered Kriging?  I have used the stk package from
Octave-forge with profit.

--
Francesco Potortì (ricercatore)        Voice:  +39.050.621.3058
ISTI - Area della ricerca CNR          Mobile: +39.348.8283.107
via G. Moruzzi 1, I-56124 Pisa         Skype:  wnlabisti
(gate 20, 1st floor, room C71)         Web:    http://fly.isti.cnr.it