function [pos_opt] = calc_pos_opt(signal,step,maxmin)
% Calculation of optima
%
% Input: signal signal
% step stepsize according to application
% maxmin for finding maxima: maxmin = 1
% for finding minima: maxmin = -1
% Output: pos_opt positions of the optima
%
% Author(s): Jonathan Moeyersons (Jonathan.Moeyersons@esat.kuleuven.be)
% Sabine Van Huffel (Sabine.Vanhuffel@esat.kuleuven.be)
% Carolina Varon (Carolina.Varon@esat.kuleuven.be)
%
% Version History:
% - 06/05/2019 JM Initial version
%
% Copyright (c) 2019, Jonathan Moeyersons, KULeuven-ESAT-STADIUS
%
% This software is made available for non commercial research purposes only
% under the GNU General Public License. However, notwithstanding any
% provision of the GNU General Public License, this software may not be
% used for commercial purposes without explicit written permission after
% contacting jonathan.moeyersons@esat.kuleuven.be
%
% This program 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 <https://www.gnu.org/licenses/>.
% Get the length of the signal
sze = length(signal);
%% Select the upward slopes
% Pre-allocate
difference = zeros(sze-1,1);
for ii = 1:sze-step
% If the amplitude of the selected sample is smaller than the amplitude
% of the selected sample plus the step size
if (signal(ii+step)-signal(ii))*maxmin > 0
difference(ii,1) = 1;
else
difference(ii,1) = 0;
end
end
% time = 1:length(signal);
% figure; plot(signal); hold on; scatter(time(difference==1),signal(difference==1))
%% Select the optima
% Pre-allocate
pos_opt = zeros(1,sze-step);
no_opt = 0;
for ii = 2:sze-step %step/2+1:sze-step
real_opt = 1;
% If you are at the end of the upwards slope
if difference(ii-1,1) == 1 && difference(ii,1) == 0
count = 1;
% Check if the upward slope lasts long enough
while real_opt == 1 && count < step && count < ii
if difference(ii-count,1) == 1
real_opt = 1;
else
real_opt = 0;
end
count = count + 1;
end
% If the upward slope is long enough
if real_opt == 1 && count >= 0.75*step
% Select the interval containing the peak
interval = ii : ii + step;
% Select the extremum in that interval
if maxmin == 1
[~,index] = max(signal(interval));
else
[~,index] = min(signal(interval));
end
% Select the position of the peak
no_opt = no_opt + 1;
pos_opt(no_opt) = interval(index);
end
end
end
pos_opt = pos_opt(1:no_opt);
% figure
% plot(signal);
% hold on
% plot(pos_opt,signal(pos_opt),'ro')
% title('Optima')