[R] Function that create day of the year column.

Frederic Ntirenganya ntfredo at gmail.com
Tue Nov 4 12:40:27 CET 2014

Dear All,

I would like to make a function that create Day of the year column in a
State of the problem: write a function that create a day column either from
a single date column (string/or factors) or from date in 3 columns (year,
month, day).

I made the following function for a single date. I would like to add a
condition for date in 3 columns (year, month, day). My data is daily
climate data.


#This function create day of teh year from a single date
column(ex:2009-08-02) or/and
#from the date in 3 columns (Year, month, Day).
  dt=yday(data$Date) # single date of the data
  datelp= dt>59 & !leap_year(data$Date)# tell us that the date occurs
during a leap year
  dt[datelp]=dt[datelp]+1 # add one for non leap_year
  cbind(data, dt) # combining columns of data
  conames(data)="DOY" # name of new column. ??I have a problem on how I can
precise the column in gerenal.

ex: year  month day   Date          Rain Tmin Tmax
      1971  1         1    1971-01-01  0        8     18
      1971   1         2   1971-01-02   1.2     3     8.2
        .       .          .         .               .       .      .
        .       .          .         .               .       .      .
        .       .          .         .               .       .      .

Any idea of how I can make this function is welcome. Thanks


Frederic Ntirenganya
Maseno University,
African Maths Initiative,
Email: fredo at aims.ac.za

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