Find max values for each year

I have a time series matrix with hourly rain data like this:

[year month day hour minute secont rain]

rain = [2008 1 12 8 0 0
2008 1 12 9 0 0
2008 1 12 10 0 0
2008 1 12 11 0 0
2008 1 12 12 0 0.2
2008 1 12 13 0 0.2
2008 1 12 14 0 1
2008 1 12 15 0 1.6
2008 1 12 16 0 2.2
2008 1 12 17 0 1.6
2008 1 12 18 0 0.8
2008 1 12 19 0 1.6
2008 1 12 20 0 0.8
2008 1 12 21 0 0.6
2008 1 12 22 0 0.6
2008 1 12 23 0 0.8
2008 1 13 0 0 0.2
2008 1 13 1 0 1];

And I need to find the max value of rain(:,7) for each year, resulting in a matrix like

max = [2008 43.2
2009 41.4
2010 30.4
2011 36.6
2012 38.0];

How can I do this on MatLab?

Answer 1

[Star Strider]

Your ‘rain’ array does not exactly match the header information you posted for it, since there are only 6 columns.

This fills in the ‘seconds’ column with a vector of zeros, then does what you requested:

rain = [2008 1 12 8 0 0
        2008 1 12 9 0 0
        2008 1 12 10 0 0
        2008 1 12 11 0 0
        2008 1 12 12 0 0.2
        2008 1 12 13 0 0.2
        2008 1 12 14 0 1
        2008 1 12 15 0 1.6
        2008 1 12 16 0 2.2
        2008 1 12 17 0 1.6
        2008 1 12 18 0 0.8
        2008 1 12 19 0 1.6
        2008 1 12 20 0 0.8
        2008 1 12 21 0 0.6
        2008 1 12 22 0 0.6
        2008 1 12 23 0 0.8
        2008 1 13 0 0 0.2
        2008 1 13 1 0 1];

Times = datetime([rain(:,1:5) zeros(size(rain,1),1)]);              % Create ‘datetime’ Array
TData = timetable(Times, rain(:,6));                                % Convert To ‘timetable’
YrMean = retime(TData, 'yearly', 'max');                            % Yearly Maximum
Max = [YrMean.Times.Year YrMean.Var1]

producing (with the posted data):

Max =
         2008          2.2

Also, don’t name it ‘max’, since that overshadows the MATLAB max function. I capitalised it here to prevent that (MATLAB is case-sensitive).

[Mahtab Moalemi]

I have a two colums array with the first column being years (1975-2020) and the second column values.

I can't get to work it out with the method you explained above.

Do I have to have day/month/year and time to be able to use the method you explained?

Could you please help me out with this?

thanks

[Star Strider]

Mahtab Moalemi —

Your Comment does not directly relate to this thread.

Please post this as a new Question, then delete your Comment.

[Mahtab Moalemi]

I have done that too! My question had the exact same title just the format was different. So it is actually related anyway.