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: plx_ts.m
    path of file: ./repos/opticka/omniplex/ReadPLX
    
    the code of the file until where you have to start completion: function [n, ts] = plx_ts(filename, channel, unit)
% plx_ts(filename, channel, unit): read spike timestamps from a .plx file
%
% [n, ts] = plx_ts(filename, channel, unit)

    
function [n, ts] = plx_ts(filename, channel, unit)
% plx_ts(filename, channel, unit): read spike timestamps from a .plx file
%
% [n, ts] = plx_ts(filename, channel, unit)
%
% INPUT:
%   filename - if empty string, will use File Open dialog
%   channel - 1-based channel number or channel name
%   unit  - unit number (0- unsorted, 1-4 units a-d)
%
% OUTPUT:
%   n - number of timestamps
%   ts - array of timestamps (in seconds)

n = 0;
ts = -1;

if nargin ~= 3
    error 'expected 3 input arguments';
end