[R] Interpolate univariate data on regular 3D grid to new 3D grid

[Gregory Jefferis]

Dear R Users,

I have some data that is very similar in form to a 3D image - ie univariate
data on a regular 3D grid.  I keep this as a 3D numeric array in R with
attributes describing the sampling points along the 3 dimensions.

I would like to interpolate this onto a new regular 3D grid that I specify
(eg by supplying 3 vectors corresponding to the new grid locations on each
of the 3 dimensions).  Interpolation methods would ideally include nearest
neighbour and linear.

The arrays can be large (> 1e7 points) so I would like this to be efficient.
I can find lots of 1d or 2d interpolation methods but no 3d ones and
anything that I write will probably take me a while to optimise.

Many thanks for any suggestions,

Greg Jefferis.
-- 
Gregory Jefferis, PhD                                   and:
Research Fellow    
Department of Zoology                                   St John's College
University of Cambridge                                 Cambridge
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United Kingdom

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