You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: xyz2uvN.m
    path of file: ./repos/PanoBasic/CoordsTransfrom
    
    the code of the file until where you have to start completion: function [ uv ] = xyz2uvN( xyz, planeID )
%XYZ2UVN Convert XYZ expression to UV expression in 3D
%   change 3-dim unit vector XYZ expression to UV in 3D

    
function [ uv ] = xyz2uvN( xyz, planeID )
%XYZ2UVN Convert XYZ expression to UV expression in 3D
%   change 3-dim unit vector XYZ expression to UV in 3D
%   planeID: base plane for UV, 1=XY
%   Check uv2xyzN for opposite mapping
if ~exist('planeID', 'var')
    planeID = 1;
end