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: enzymeUsage.m
    path of file: ./repos/GECKO/src/geckomat/utilities
    
    the code of the file until where you have to start completion: function usageData = enzymeUsage(ecModel,fluxes,zero)
% enzymeUsage
%   Gives enzyme usages based on a provided flux distribution, as obtained
%   from a full GECKO model. It can give:
%   1)  absolute usage: the specific enzyme usage in ug/gDCW/h, which can
%       be given for enzymes with- and without concentration information;
%   2)  capacity usage: the ratio of available enzyme that is used, calcuted
%       by (absUsage/UB) (note that capacity usage is 0 if an enzyme
%       concentration was not constrained in the model);
%   3)  UB: the upper bound of each enzyme exchange reaction, which may not
%       be the same as the enzyme concentration, if it has been
%       flexibilized
%   4)  protID: the protein identifiers for each enzyme (if the model has an
%       enzymes field than this order is used, otherwise it is given
%       alphabetically.
%
% Input:
%   ecModel     an ecModel in GECKO 3 format (with ecModel.ec structure)
%   fluxes      vector of fluxes, for instance sol.x
%   zero        logical whether also enzymes with zero absolute usage
%               should be included (Optional, default true)
%
% Output:
%   usageData   structure with enzyme usage data
%               capUsage    vector of enzyme capacity usages
%               absUsage    vector of absolute enzyme usages
%               UB          vector of enzyme exchange reaction upper bounds
%               protID      string array of matching protein IDs
%
% Usage:
%   usageData = enzymeUsage(ecModel,fluxes,zero)

    
function usageData = enzymeUsage(ecModel,fluxes,zero)
% enzymeUsage
%   Gives enzyme usages based on a provided flux distribution, as obtained
%   from a full GECKO model. It can give:
%   1)  absolute usage: the specific enzyme usage in ug/gDCW/h, which can
%       be given for enzymes with- and without concentration information;
%   2)  capacity usage: the ratio of available enzyme that is used, calcuted
%       by (absUsage/UB) (note that capacity usage is 0 if an enzyme
%       concentration was not constrained in the model);
%   3)  UB: the upper bound of each enzyme exchange reaction, which may not
%       be the same as the enzyme concentration, if it has been
%       flexibilized
%   4)  protID: the protein identifiers for each enzyme (if the model has an
%       enzymes field than this order is used, otherwise it is given
%       alphabetically.
%
% Input:
%   ecModel     an ecModel in GECKO 3 format (with ecModel.ec structure)
%   fluxes      vector of fluxes, for instance sol.x
%   zero        logical whether also enzymes with zero absolute usage
%               should be included (Optional, default true)
%
% Output:
%   usageData   structure with enzyme usage data
%               capUsage    vector of enzyme capacity usages
%               absUsage    vector of absolute enzyme usages
%               UB          vector of enzyme exchange reaction upper bounds
%               protID      string array of matching protein IDs
%
% Usage:
%   usageData = enzymeUsage(ecModel,fluxes,zero)

if nargin<3
    zero=true;
end