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: createGMMmask.m
    path of file: ./repos/pcm/matlab/src
    
    the code of the file until where you have to start completion: function MASK = createGMMmask(LSmask,FIELD,DPT,varargin)
% createGMMmask Create a mask from land/sea and 3D field data constraints

    
function MASK = createGMMmask(LSmask,FIELD,DPT,varargin)
% createGMMmask Create a mask from land/sea and 3D field data constraints
%
% MASK = createGMMmask(LSmask,FIELD,DPT) 
% This function will create a mask with:
% - 1 where LSmask is 1 & FIELD is 1 at first level
% - 0 elsewehere
%
% MASK = createGMMmask(LSmask,FIELD,DPT,'Zmin',VALUE) 
% This function will create a mask with:
% - 1 where LSmask is 1 & FIELD is 1 at all levels above minimum depth VALUE
% - 0 elsewehere
%
% Inputs:
% 	LSmask (lat/lon): A lat/lon mask field with 0/1 values
% 	FIELD: The dpt/lat/lon 3D field to use for 0/1 extraction
% 	DPT: The vertical axis (negative, downward) of FIELD
% Options:
% 	Zmin: A minimum depth for FIELD values to be defined (0 by default)
%
% Outputs:
% 	MASK: A (lat/lon) mask field of 0/1 values with 1 where data should be kept for classification 
%
% PCM is Profile Classification Modelling
% Copyright (C) 2015-2017,  OBIDAM Developpers
% For more information, see http://github.com/obidam/pcm
% Created: 2015-11-18 (G. Maze, Ifremer, Laboratoire d'Oc√©anographie Physique et Spatiale)

% This file is part of OBIDAM/PCM.
%     OBIDAM/PCM is free software: you can redistribute it and/or modify
%     it under the terms of the GNU General Public License as published by
%     the Free Software Foundation, either version 3 of the License, or
%     (at your option) any later version.
%     OBIDAM/PCM is distributed in the hope that it will be useful,
%     but WITHOUT ANY WARRANTY; without even the implied warranty of
%     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
%     GNU General Public License for more details.
%     You should have received a copy of the GNU General Public License
%     along with Foobar.  If not, see <http://www.gnu.org/licenses/>.

%- Init
Zmin = 0;

%- Load user options:
if nargin-3 > 0
	if mod(nargin-3,2) ~= 0
		error('Options must come in pairs: OPTION,VALUE')
	end