Transform year/day colnames into date in r

Question

I have the following columns' names of dataframe in year/day format

colnames(ndvi.df)
 [1] "gid"     "xcoord"  "ycoord"  "col"     "row"     "gwno"    "country" "km2"    
 [9] "2000049" "2000065" "2000081" "2000097" "2000113" "2000129" "2000145" "2000161"
[17] "2000177" "2000193" "2000209" "2000225" "2000241" "2000257" "2000273" "2000289"
[25] "2000305" "2000321" "2000337" "2000353"

How can I transform them into the corresponding year-month_day format please ?

Example: 2000049 = 18/02/2000

https://stackoverflow.com/questions/24200014/convert-day-of-year-to-date seems to be a duplicate — Gabe Solomon, Jun 28 '22 at 20:37
I don't think so. It does not seem to be a duplicate regarding my context. — Myr TH, Jun 29 '22 at 07:18
@MohamedDesouky year 2000 and day 49 of the year = 18/02/2000 — Myr TH, Jun 29 '22 at 07:20

score 1 · Accepted Answer · answered Jun 28 '22 at 20:37

1

You can use lubridate

library(lubridate)
cols = colnames(ndvi.df)
ymd(parse_date_time(cols[9:length(cols)], orders="yj"))

Output:

 [1] "2000-02-18" "2000-03-05" "2000-03-21" "2000-04-06" "2000-04-22" "2000-05-08" "2000-05-24" "2000-06-09"
 [9] "2000-06-25" "2000-07-11" "2000-07-27" "2000-08-12" "2000-08-28" "2000-09-13" "2000-09-29" "2000-10-15"
[17] "2000-10-31" "2000-11-16" "2000-12-02" "2000-12-18"

answered Jun 28 '22 at 20:37

langtang

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Thank you !!! but how to integrate it directly to the initial dataframe ? – Myr TH Jun 29 '22 at 07:19
I tried this but does not work ==> cols = ymd(parse_date_time(cols[9:length(cols)], orders="yj")) colnames(ndvi.df[,9:28]) = cols – Myr TH Jun 29 '22 at 07:40
OK found it: names(ndvi.df2)[9:28] = paste(cols) – Myr TH Jun 29 '22 at 09:44

Transform year/day colnames into date in r

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