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: m_coord.m
    path of file: ./repos/matlab_owc/lib/m_map1.4
    
    the code of the file until where you have to start completion: function coordsys=m_coord(coordsys);
% M_COORD Initializes the coordinate system for varous conversions.
%
%   M_COORD('set') tells you the current coordinate system
%   M_COORD('get') gives you the current possibilities
%   M_COORD(SYSTEM) sets the coordinate system to SYSTEM.
%
%   Currently the available coordinate systems are:
%              'geographic' (usual lat/long)
%              'geomagnetic' (referenced to magnetic poles)

% Rich Pawlowicz (rich@ocgy.ubc.ca) nOV/2001
%
% This software is provided "as is" without warranty of any kind. But
% it's mine, so you can't sell it.


    
function coordsys=m_coord(coordsys);
% M_COORD Initializes the coordinate system for varous conversions.
%
%   M_COORD('set') tells you the current coordinate system
%   M_COORD('get') gives you the current possibilities
%   M_COORD(SYSTEM) sets the coordinate system to SYSTEM.
%
%   Currently the available coordinate systems are:
%              'geographic' (usual lat/long)
%              'geomagnetic' (referenced to magnetic poles)

% Rich Pawlowicz (rich@ocgy.ubc.ca) nOV/2001
%
% This software is provided "as is" without warranty of any kind. But
% it's mine, so you can't sell it.


global MAP_COORDS

if nargin==0, coordsys='usage'; end