# I have air temperature dataset obtained in every 30 minutes for a day for a whole year. I want to extract maximum and minimum air temperature for each day for a year (365 days).

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Erasmus Sowah on 19 Mar 2018
Commented: Akira Agata on 21 Mar 2018
Data=importtemp ('observed.csvc');
Data1=Data ([1:end],1); % air temp
Do=datenum ([2013,0101 000]); date started
Dv=Do + [1/24:1/24:365]'; % number vector
Ds=datestr (Dv,'01.01.2013'); date string
T=([1/24:1/24:365])+randn (size (Dv')); %
Data1={Ds T'}

pankaj singh on 20 Mar 2018
You can separate your data into days and then use max() and min() matlab functions to find the maximum and minimum temperatures.

Akira Agata on 20 Mar 2018
By using timetable and retime function, you can do that very easily. The following is an example:
% Sample data
Time = (datetime(2017,1,1,0,0,0):minutes(30):datetime(2017,3,31,23,30,0))';
AirTemp = 20 + 10*rand(numel(Time),1);
% Create timetable
TT = timetable(Time,AirTemp);
% Daily min/max can be calculated by retime function like this
dailyMax = retime(TT,'daily','max');
dailyMin = retime(TT,'daily','min');
Erasmus Sowah on 20 Mar 2018
Ok, thank you boss, but my data length is 17520 because every 30 minutes in a day data is collected; so for a day 48 different values are obtained.
Akira Agata on 21 Mar 2018
It's not clear for me what is the problem. The script can run even when the data length is 17520. Please try and see by changing the first line with this:
Time = (datetime(2017,1,1,0,0,0):minutes(30):datetime(2017,1,1,0,0,0)+minutes(30)*(17520-1))';