% -*- texinfo -*-
% @deftypefn {Function File} {@var{zi} =} interp2 (@var{x}, @var{y}, @var{z}, @var{xi}, @var{yi})
% @deftypefnx {Function File} {@var{zi} =} interp2 (@var{Z}, @var{xi}, @var{yi})
% @deftypefnx {Function File} {@var{zi} =} interp2 (@var{Z}, @var{n})
% @deftypefnx {Function File} {@var{zi} =} interp2 (@dots{}, @var{method})
% @deftypefnx {Function File} {@var{zi} =} interp2 (@dots{}, @var{method}, @var{extrapval})
%
% Two-dimensional interpolation. @var{x}, @var{y} and @var{z} describe a
% surface function. If @var{x} and @var{y} are vectors their length
% must correspondent to the size of @var{z}. @var{x} and @var{y} must be
% monotonic. If they are matrices they must have the @code{meshgrid}
% format.
%
% @table @code
% @item interp2 (@var{x}, @var{y}, @var{Z}, @var{xi}, @var{yi}, @dots{})
% Returns a matrix corresponding to the points described by the
% matrices @var{xi}, @var{yi}.
%
% If the last argument is a string, the interpolation method can
% be specified. The method can be 'linear', 'nearest' or 'cubic'.
% If it is omitted 'linear' interpolation is assumed.
%
% @item interp2 (@var{z}, @var{xi}, @var{yi})
% Assumes @code{@var{x} = 1:rows (@var{z})} and @code{@var{y} =
% 1:columns (@var{z})}
%
% @item interp2 (@var{z}, @var{n})
% Interleaves the matrix @var{z} n-times. If @var{n} is omitted a value
% of @code{@var{n} = 1} is assumed.
% @end table
%
% The variable @var{method} defines the method to use for the
% interpolation. It can take one of the following values
%
% @table @asis
% @item 'nearest'
% Return the nearest neighbor.
% @item 'linear'
% Linear interpolation from nearest neighbors.
% @item 'pchip'
% Piece-wise cubic hermite interpolating polynomial (not implemented yet).
% @item 'cubic'
% Cubic interpolation from four nearest neighbors.
% @item 'spline'
% Cubic spline interpolation--smooth first and second derivatives
% throughout the curve.
% @end table
%
% If a scalar value @var{extrapval} is defined as the final value, then
% values outside the mesh as set to this value. Note that in this case
% @var{method} must be defined as well. If @var{extrapval} is not
% defined then NA is assumed.
%
% @seealso{interp1}
% @end deftypefn