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
Erasmus Sowah 2018-3-19
评论： Akira Agata 2018-3-21
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'}

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回答（2 个）

pankaj singh
pankaj singh 2018-3-20
You can separate your data into days and then use max() and min() matlab functions to find the maximum and minimum temperatures.
Akira Agata
Akira Agata 2018-3-20
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');
  2 个评论
Erasmus Sowah
Erasmus Sowah 2018-3-20
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
Akira Agata 2018-3-21
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))';

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