% -*- texinfo -*-
% @deftypefn {Function File} {@var{vi} =} interp3 (@var{x}, @var{y},@var{z}, @var{v}, @var{xi}, @var{yi}, @var{zi})
% @deftypefnx {Function File} {@var{vi} =} interp3 (@var{v}, @var{xi}, @var{yi}, @var{zi})
% @deftypefnx {Function File} {@var{vi} =} interp3 (@var{v}, @var{m})
% @deftypefnx {Function File} {@var{vi} =} interp3 (@var{v})
% @deftypefnx {Function File} {@var{vi} =} interp3 (@dots{}, @var{method})
% @deftypefnx {Function File} {@var{vi} =} interp3 (@dots{}, @var{method}, @var{extrapval})
%
% Perform 3-dimensional interpolation. Each element of the 3-dimensional
% array @var{v} represents a value at a location given by the parameters
% @var{x}, @var{y}, and @var{z}. The parameters @var{x}, @var{x}, and
% @var{z} are either 3-dimensional arrays of the same size as the array
% @var{v} in the 'meshgrid' format or vectors. The parameters @var{xi}, etc.
% respect a similar format to @var{x}, etc., and they represent the points
% at which the array @var{vi} is interpolated.
%
% If @var{x}, @var{y}, @var{z} are omitted, they are assumed to be
% @code{x = 1 : size (@var{v}, 2)}, @code{y = 1 : size (@var{v}, 1)} and
% @code{z = 1 : size (@var{v}, 3)}. If @var{m} is specified, then
% the interpolation adds a point half way between each of the interpolation
% points. This process is performed @var{m} times. If only @var{v} is
% specified, then @var{m} is assumed to be @code{1}.
%
% Method is one of:
%
% @table @asis
% @item 'nearest'
% Return the nearest neighbor.
% @item 'linear'
% Linear interpolation from nearest neighbors.
% @item 'cubic'
% Cubic interpolation from four nearest neighbors (not implemented yet).
% @item 'spline'
% Cubic spline interpolation--smooth first and second derivatives
% throughout the curve.
% @end table
%
% The default method is 'linear'.
%
% If @var{extrap} is the string 'extrap', then extrapolate values beyond
% the endpoints. If @var{extrap} is a number, replace values beyond the
% endpoints with that number. If @var{extrap} is missing, assume NA.
% @seealso{interp1, interp2, spline, meshgrid}
% @end deftypefn