Creating a single timestamp from separate DAY OF YEAR, Year and Time columns in R

Question

I have a time series dataset for several meteorological variables. The time data is logged in three separate columns:

1. Year (e.g. 2012)
2. Day of year (e.g. 261 representing 17-September in a Leap Year)
3. Hrs:Mins (e.g. 1610)

Is there a way I can merge the three columns to create a single timestamp in R? I'm not very familiar with how R deals with the Day of Year variable.

Thanks for any help with this!

Answer 1

It looks like the timeDate package can handle gregorian time frames. I haven't used it personally but it looks straightforward. There is a shift argument in some methods that allow you to set the offset from your data.

http://cran.r-project.org/web/packages/timeDate/timeDate.pdf

Because you mentioned it, I thought I'd show the actual code to merge together separate columns. When you have the values you need in separate columns you can use paste to bring them together and lubridate::mdy to parse them.

library(lubridate)

col.month <- "Jan"
col.year <- "2012"
col.day <- "23"

date <- mdy(paste(col.month, col.day, col.year, sep = "-"))

Lubridate is a great package, here's the official page: https://github.com/hadley/lubridate

And here is a nice set of examples: http://www.r-statistics.com/2012/03/do-more-with-dates-and-times-in-r-with-lubridate-1-1-0/

Answer 2

You should get quite far using ISOdatetime. This function takes vectors of year, day, hour, and minute as input and outputs an POSIXct object which represents time. You just have to split the third column into two separate hour minute columns and you can use the function.