hello
my 2 cents suggestion
[num,txt,raw] = xlsread('time_data.xlsx') ;
timeday = num(:,1); % time expressed in fraction of a day 24 hours
data = num(:,2);
time_s = timeday*24*3600;
samples = length(time_s);
dt = (time_s(end)-time_s(1))/(samples-1);
% t = (0:dt:(samples-1)*dt); % new time vector (unique values)
Fs = 1/dt;
% main loop : extract min max vales for every 5 min data %
buffer_in_minutes = 5; % put minutes here
buffer_size = floor(buffer_in_minutes*60/dt);
for ci = 1:floor(samples/buffer_size)
ind_start = 1+(ci-1)*buffer_size;
ind_stop = ind_start + buffer_size;
data_tmp = data(ind_start:ind_stop);
min_val(ci) = min(data_tmp);
max_val(ci) = max(data_tmp);
sum_val(ci) = sum(data_tmp);
time_index_s(ci) = mean(time_s(ind_start:ind_stop));
end
% x are you seconds values
s = seconds(time_index_s);
% Change the duration format to hh:mm
s.Format = 'hh:mm:ss';
figure(1);
plot(s,min_val,'+',s,max_val,'+',s,sum_val,'+');grid
