How to convert irregular daily data to annual data?

Hi All!

I have a dataset (excel file attached - pcr.xlsx) of daily data values. The values are expressed as "Tonnes". I wanted to convert these to annual data from 1959 till date. My issue is that the daily data are irregular i.e. each year does not contain 365/366 values, so I am confused on how to directly get the answer (if each year had constant number of data points - 365, I think it would be easier).

I did try the "convert2annual" function but had no luck with it. I would appreciate some help in this regard. Thank you!

Answer 1

[Chunru]

T = readtable("https://www.mathworks.com/matlabcentral/answers/uploaded_files/1101770/pcr.xlsx");
T(T.Tonnes == 0, :) =[];   % remove rows where Tonnes == 0

head(T)

ans = 8×2 table
        Dates         Tonnes
    ______________    ______

    {'25-07-1959'}    319.76
    {'25-07-1959'}    319.76
    {'25-07-1959'}    4268.3
    {'25-07-1959'}    2926.8
    {'25-07-1959'}    3963.4
    {'25-07-1959'}    1585.4
    {'25-07-1959'}     975.7
    {'25-07-1959'}    1524.4

T1  = timetable(datetime(T.Dates, "InputFormat", 'dd-MM-yyyy'), T.Tonnes);
T1.Properties.VariableNames = "Tonnes";
T2 = retime(T1, 'yearly', 'mean')

T2 = 61×1 timetable
       Time        Tonnes
    ___________    ______

    01-Jan-1959    1425.8
    01-Jan-1960    2580.8
    01-Jan-1961    1813.5
    01-Jan-1962    2659.8
    01-Jan-1963    1656.8
    01-Jan-1964    1409.7
    01-Jan-1965    1727.9
    01-Jan-1966    1271.6
    01-Jan-1967    1430.1
    01-Jan-1968    1102.1
    01-Jan-1969    1678.4
    01-Jan-1970    1316.5
    01-Jan-1971    1369.1
    01-Jan-1972    1329.6
    01-Jan-1973    1031.2
    01-Jan-1974    1420.3

[Keegan Carvalho]

Thanks @Chunru for your answer. However, there's a slight issue. I have re-attached the file here.

In the "Tonnes" column, there are zeros, so I wanted to take the annual mean by ignoring the zeros. I tried splitting the columns and used:

tonnes(tonnes==0) = []

But this eliminated the rows in the process. Could you please help me in calculating the annual means by ignoring the zeros in the "Tonnes" column?

[Chunru]

You can remove those rows in table before retime as updated above.

[Keegan Carvalho]

Thanks you @Chunru I understood where I went wrong.