determine index of a value (monthly) from excel table

Hi.. how i can determine index monthly mean for time series each years i have ponit every houer so in one day i have 24 points and each month i have difrrent number of points , like Jan 24x31=744 , Feb 24x28=672... I find some months incomplete

Answer 1

[Peter Perkins]

If you are using R2016b or later, use a timetable, and call retime to compute a monthly mean. Even prior to 16b, you should use a table with a datetime variable in it, and use varfun to compute the mean with month as the grouping variable.

[nada]

may you give me example

example table in my work

[Peter Perkins]

Your example spreadsheet has data from one month. But in any case, all you need is readtable, table2timetable, and retime.

>> t = readtable('data exsample.xls')
Warning: Variable names were modified to make them valid MATLAB identifiers. The original names are saved in the
VariableDescriptions property. 
t =
  18×3 table
     Jday           Datetime          WL_m_
    ______    ____________________    _____
    0.0417    01-Jan-2008 00:00:00    4.42 
    0.0833    01-Jan-2008 01:00:00    4.17 
     0.125    01-Jan-2008 02:00:00    3.95 
    0.1667    01-Jan-2008 03:00:00    3.76 
    0.2083    01-Jan-2008 04:00:00    3.61 
      0.25    01-Jan-2008 05:00:00     3.6 
    0.2917    01-Jan-2008 06:00:00    3.66 
    0.3333    01-Jan-2008 07:00:00    3.83 
     0.375    01-Jan-2008 08:00:00    4.04 
    0.4167    01-Jan-2008 09:00:00    4.25 
    0.4583    01-Jan-2008 10:00:00    4.38 
       0.5    01-Jan-2008 11:00:00    4.37 
    0.5417    01-Jan-2008 12:00:00    4.27 
    0.5833    01-Jan-2008 13:00:00    4.12 
     0.625    01-Jan-2008 14:00:00    3.94 
    0.6667    01-Jan-2008 15:00:00    3.81 
    0.7083    01-Jan-2008 16:00:00     3.7 
      0.75    01-Jan-2008 17:00:00    3.69 
>> tt = table2timetable(t,'RowTimes','Datetime')
tt =
  18×2 timetable
          Datetime           Jday     WL_m_
    ____________________    ______    _____
    01-Jan-2008 00:00:00    0.0417    4.42 
    01-Jan-2008 01:00:00    0.0833    4.17 
    01-Jan-2008 02:00:00     0.125    3.95 
    01-Jan-2008 03:00:00    0.1667    3.76 
    01-Jan-2008 04:00:00    0.2083    3.61 
    01-Jan-2008 05:00:00      0.25     3.6 
    01-Jan-2008 06:00:00    0.2917    3.66 
    01-Jan-2008 07:00:00    0.3333    3.83 
    01-Jan-2008 08:00:00     0.375    4.04 
    01-Jan-2008 09:00:00    0.4167    4.25 
    01-Jan-2008 10:00:00    0.4583    4.38 
    01-Jan-2008 11:00:00       0.5    4.37 
    01-Jan-2008 12:00:00    0.5417    4.27 
    01-Jan-2008 13:00:00    0.5833    4.12 
    01-Jan-2008 14:00:00     0.625    3.94 
    01-Jan-2008 15:00:00    0.6667    3.81 
    01-Jan-2008 16:00:00    0.7083     3.7 
    01-Jan-2008 17:00:00      0.75    3.69 
>> retime(tt,'monthly','mean')
ans =
  1×2 timetable
          Datetime           Jday      WL_m_ 
    ____________________    _______    ______
    01-Jan-2008 00:00:00    0.39583    3.9761
>>

[nada]

Thank you a lot Peter