# interp3d

3d spline evaluation function

### Syntax

[fp[,dfpdx,dfpdy,dfpdz]]=interp3d(xp,yp,zp,tl,out_mode)

### Arguments

- xp, yp, zp
real vectors or matrices of same size

- tl
tlist of type "splin3d", defining a 3d tensor spline (called

`s`

in the following)- out_mode
(optional) string defining the evaluation of

`s`

outside the grid ([xmin,xmax]x[ymin,ymax]x[zmin,zmax])- fp
vector or matrix of same format than

`xp`

,`yp`

and`zp`

, elementwise evaluation of`s`

on these points.- dfpdx, dfpdy, dfpdz
vectors (or matrices) of same format than

`xp`

,`yp`

and`zp`

, elementwise evaluation of the first derivatives of`s`

on these points.

### Description

Given a tlist `tl`

defining a 3d spline function
(see splin3d) this function evaluates
*s* (and *ds/dx, ds/dy, ds/dz* if
needed) at *(xp(i),yp(i),zp(i))* :

The `out_mode`

parameter defines the evaluation
rule for extrapolation, i.e. for *(xp(i),yp(i),zp(i)) not in
[xmin,xmax]x[ymin,ymax]x[zmin,zmax]*
:

- "by_zero"
an extrapolation by zero is done

- "by_nan"
extrapolation by Nan

- "C0"
the extrapolation is defined as follows :

- "periodic"
`s`

is extended by periodicity.

### Examples

`// see the examples of the splin3d help page`

### See also

- splin3d — spline gridded 3d interpolation
- bsplin3val — 3d spline arbitrary derivative evaluation function

### History

Version | Description |

5.4.0 | previously, imaginary part of input arguments were implicitly ignored. |

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