R convert date to day of the year

Question

I have a data frame as follows

S = c("28/05/2016 07:00", "29/05/2016 07:00", "30/05/2016 07:00")
S1 = c("2016-05-28", "2016-05-29", "2016-05-30") 
df = data.frame(S, S1)

I want to convert the dates to day of the year. Using

df$Day_S <- yday(df$S)
df$Day_S1 <- yday(df$S1)

gives

    S                  S1            Day_S   Day_S1
1   28/05/2016 07:00   2016-05-28    141     149
2   29/05/2016 07:00   2016-05-29    140     150
3   30/05/2016 07:00   2016-05-30    140     151

which works only for the format of the 'S1' dates.

Ive tried

df$S_1 <- format(as.POSIXct(df$S,format='%d/%m/%Y'),format='%d/%m/%Y')
df$Day_S_1 <- yday(df$S_1)

but this still gives the wrong day of the year.

How can i convert the 'S' column to day of the year?

You just forgot the time, i.e. `yday(as.POSIXct(S, format = '%d/%m/%Y %H:%M'))` should work — Sotos, Mar 28 '17 at 08:42

score 5 · Accepted Answer · answered Mar 28 '17 at 08:42

5

This works for me

S = c("28/05/2016 07:00", "29/05/2016 07:00", "30/05/2016 07:00")
s_1 <- as.Date(S,format='%d/%m/%Y')
Day_S <- lubridate::yday(s_1)

answered Mar 28 '17 at 08:42

Morgan Ball

760
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23

1

Instead of "lubridate" function you can also use strftime funstion: `Day_S <- strftime(s_1, format = "%j")` – Ursulka Siete Nov 05 '18 at 14:17

R convert date to day of the year

1 Answers1