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: WL_scal2frq.m
    path of file: ./repos/hctsa/Operations
    
    the code of the file until where you have to start completion: function out = WL_scal2frq(y, wname, amax, delta)
% WL_scal2frq   Frequency components in a periodic time series
%
% Estimates frequency components using functions from Matlab's Wavelet Toolbox,
% including the scal2frq function.
%
%---INPUTS:
% y, the input time series
%
% wname, the name of the mother wavelet to analyze the data with: e.g., 'db3',
%           'sym2', cf. Wavelet Toolbox Documentation for details
%
% amax, the maximum scale / level (can be 'max' to set according to wmaxlev)
%
% delta, the sampling period
%
%---OUTPUTS: the level with the highest energy coefficients, the dominant
% period, and the dominant pseudo-frequency.
%
% Adapted from example in Matlab Wavelet Toolbox documentation. It's kind of a
% weird idea to apply the method to generic time series.

% ------------------------------------------------------------------------------
% Copyright (C) 2020, Ben D. Fulcher <ben.d.fulcher@gmail.com>,
% <http://www.benfulcher.com>
%
% If you use this code for your research, please cite the following two papers:
%
% (1) B.D. Fulcher and N.S. Jones, "hctsa: A Computational Framework for Automated
% Time-Series Phenotyping Using Massive Feature Extraction, Cell Systems 5: 527 (2017).
% DOI: 10.1016/j.cels.2017.10.001
%
% (2) B.D. Fulcher, M.A. Little, N.S. Jones, "Highly comparative time-series
% analysis: the empirical structure of time series and their methods",
% J. Roy. Soc. Interface 10(83) 20130048 (2013).
% DOI: 10.1098/rsif.2013.0048
%
% This function 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.
%
% This program 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
% this program. If not, see <http://www.gnu.org/licenses/>.
% ------------------------------------------------------------------------------

% ------------------------------------------------------------------------------
%% Check that a Wavelet Toolbox license is available:
% ------------------------------------------------------------------------------
BF_CheckToolbox('wavelet_toolbox')

% ------------------------------------------------------------------------------
%% Preliminaries

    
function out = WL_scal2frq(y, wname, amax, delta)
% WL_scal2frq   Frequency components in a periodic time series
%
% Estimates frequency components using functions from Matlab's Wavelet Toolbox,
% including the scal2frq function.
%
%---INPUTS:
% y, the input time series
%
% wname, the name of the mother wavelet to analyze the data with: e.g., 'db3',
%           'sym2', cf. Wavelet Toolbox Documentation for details
%
% amax, the maximum scale / level (can be 'max' to set according to wmaxlev)
%
% delta, the sampling period
%
%---OUTPUTS: the level with the highest energy coefficients, the dominant
% period, and the dominant pseudo-frequency.
%
% Adapted from example in Matlab Wavelet Toolbox documentation. It's kind of a
% weird idea to apply the method to generic time series.

% ------------------------------------------------------------------------------
% Copyright (C) 2020, Ben D. Fulcher <ben.d.fulcher@gmail.com>,
% <http://www.benfulcher.com>
%
% If you use this code for your research, please cite the following two papers:
%
% (1) B.D. Fulcher and N.S. Jones, "hctsa: A Computational Framework for Automated
% Time-Series Phenotyping Using Massive Feature Extraction, Cell Systems 5: 527 (2017).
% DOI: 10.1016/j.cels.2017.10.001
%
% (2) B.D. Fulcher, M.A. Little, N.S. Jones, "Highly comparative time-series
% analysis: the empirical structure of time series and their methods",
% J. Roy. Soc. Interface 10(83) 20130048 (2013).
% DOI: 10.1098/rsif.2013.0048
%
% This function 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.
%
% This program 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
% this program. If not, see <http://www.gnu.org/licenses/>.
% ------------------------------------------------------------------------------

% ------------------------------------------------------------------------------
%% Check that a Wavelet Toolbox license is available:
% ------------------------------------------------------------------------------
BF_CheckToolbox('wavelet_toolbox')

% ------------------------------------------------------------------------------
%% Preliminaries
% ------------------------------------------------------------------------------
doplot = 0; % plot outputs to figure
N = length(y); % length of the time series

% ------------------------------------------------------------------------------
%% Check Inputs
% ------------------------------------------------------------------------------
if nargin < 2 || isempty(wname)
    fprintf(1,'Wavelet not specified -- using the default db3 wavelet\n');
    wname = 'db3';
end