Timetable Monthly Average over Many Years

I have a daily precipitation data file with two columns.The first column is "date", with date format yyyy-mm-dd and the second column is "precip" with double format. My data ranges from 1980-01-01 to 2010-12-31, and I would like to determine the average precipitation values for each month over that interval.

Example of desired result:

Month avgPrecip

Jan 0.0056

Feb 0.0034

...

for each month.

I have attached my csv file with the data and my current progess. I can get the monthly average of the data within each year using a timetable and retime, but I am stuck trying to average the monthly average data for the entire data range. Thank you!

    precip = readtable('CR_precip.csv');
    precip = table2timetable(precip);
    monthlyAvg = retime(precip,'monthly','mean');

Answer 1

[Guillaume]

The easiest:

precip = table2timetable(readtable('CR_precip.csv'));
monthlyavg = groupsummary(precip, 'day', 'monthofyear', 'mean')

[Nathan Gjersvik]

This works and is very simple! Thank you very much!

[Ritesh]

hi @Guillaume, how I can use same thing in a table having 6 variables.

with this code I am getting follwing error:

Error using matlab.internal.math.checkDataVariables (line 59)

Invalid grouping variables.

Error in matlab.internal.math.parseGroupVars (line 14)

[groupVars,T] = matlab.internal.math.checkDataVariables(T,groupVars,messageIdent,'Group');

Error in groupsummary (line 172)

[groupingData,groupVars] = matlab.internal.math.parseGroupVars(groupVars,tableFlag,'groupsummary',T);

[Manoj Kumar]

Please take a look at the variables used in the CR_precip.csv file. The time/date in the timetable is defined as 'day'. If you make the call based on this, the function call should work. I hope this helps

Answer 2

[QuanCCC]

you can simply make another column of year-month-day-time, merge it to your data. Then transform it to timetable, time column will be your new column. Then use the same 'monthly','mean' on all months.

t1 = datetime(1980,01,01,12,0,0);
t2 = datetime(2010,12,31,12,0,0);
t = t1:t2;
t = t';
clear t1 t2
NewData = timetable(t, YourOldData); % merge data
MonthlyAve = retime(NewData, 'monthly', 'mean'); 

Answer 3

[Akira Agata]

Looking at your csv data, some additional options will be needed.

(1) To specify the delimiter in your csv data, 'Delimiter' option should be added in readtabe function

(2) 'Format' option should be added in datetime function

The following is an example:

T = readtable('CR_precip.csv','Delimiter',',');
T.day = datetime(T.day,'Format','MM/dd/yyyy');

TT = table2timetable(T);
TT = retime(TT,'monthly','mean');