Timetable_Averaging values from each month

Timetable Averaging values from each month(Jan-Dec) from all years between 2000-2020. So I would like to have 12 USDM_Index values; one for each month over the 21 years

[Scott MacKenzie]

If your data are in a timetable, then use the retime function with 'monthly' as the newTimeStep. Check the documentation for retime for some examples.

[Leulaye Maskal]

I have tried that but its gives me the mean for each month within each yearh so I end up wit 12 * 21 for each month

[Ritesh]

monthlyavg = groupsummary(b, 'month', 'monthofyear', 'mean');

%here b is your table

Answer 1

[Kelly Kearney]

I don't believe you can use retime to build a climatology; for that, I usually use the splitapply function. Unfortunately, splitapply's syntax for tables and timetables is very clunky (there's no easy way to apply the same function to all variables), hence my casting to and from arrays in the following example:

% The original timetable

T = timetable(datetime(2000,1:24,1)', rand(24,1), rand(24,1), ...
    'VariableNames', {'USDM_index', 'other'});

% Calculate climatological monthly average

[g, mn] = findgroups(month(T.Time));
xclim = splitapply(@(x) mean(x,1), table2array(T), g);

% Reformat to timetable

refyr = min(year(T.Time)); % ... or whatever you want
Tclim = array2timetable(xclim, 'RowTimes', datetime(refyr,mn,1), ...
    'VariableNames', T.Properties.VariableNames);

Answer 2

[Duncan Po]

Use groupsummary with 'monthofyear' binning

T = timetable(datetime(2000,1:(12*21),1)', rand(12*21,1), 'VariableNames', {'USDM_index'});
S = groupsummary(T, 'Time', 'monthofyear', 'mean')

S = 12×3 table
    monthofyear_Time    GroupCount    mean_USDM_index
    ________________    __________    _______________

           1                21            0.44367    
           2                21            0.44095    
           3                21            0.52971    
           4                21            0.66029    
           5                21            0.45509    
           6                21            0.59956    
           7                21            0.56916    
           8                21            0.49774    
           9                21            0.49873    
           10               21            0.49883    
           11               21            0.48883    
           12               21            0.56189    

[Leulaye Maskal]

I tried this but i keep getting a timetavble error