[R] Convert Long DOY time format to yyyymmdd hh format

[Enrico Schumann]

Quoting Ogbos Okike <giftedlife2014 using gmail.com>:

> Dear Experts,
> I have a data spanning 56 years from 1963 to 2018.
> The datetime format is in DOY hour:
> 1963 335 0
> 1963 335 1
> 1963 335 2
> 1963 335 3
> 1963 335 4
> 1963 335 5
> 1963 335 6
> 1963 335 7
> 1963 335 8
> 1963 335 9
> 1996 202 20
> 1996 202 21
> 1996 202 22
> 1996 202 23
> 1996 203 0
> 1996 203 1
> 1996 203 2
> 1996 203 3
> 2018 365 20
> 2018 365 21
> 2018 365 22
> 2018 365 23
> When I used:
> as.Date(335,origin="1963-01-01"), for the first row, I got:
> [1] "1963-12-02"
> This is the format I want, though it is not yet complete. Time is missing.
>
> Again, I can't be doing this one after the other. I guess you have a
> better way of handling this. I have spent some time trying to get it
> right but I am really stuck. I would be most glad if you could spare
> your busy time to help me again.
>
> Thank you very much for your usual kind assistance.
>
> Best regards
> Ogbos
>

Perhaps something like this:

read.table(text="
1963 335 0
1963 335 1
1963 335 2
1963 335 3
1963 335 4
1963 335 5
1963 335 6
1963 335 7
1963 335 8
1963 335 9
1996 202 20
1996 202 21
1996 202 22
1996 202 23
1996 203 0
1996 203 1
1996 203 2
1996 203 3
2018 365 20
2018 365 21
2018 365 22
2018 365 23
", header = FALSE, sep = " ") -> data

as.POSIXct(paste(as.Date(paste0(data[[1]], "-1-1")) + data[[2]] - 1,  
data[[3]]),
            format = "%Y-%m-%d %H")

You might want to specify a different timezone, and also check for  
"off-by-one" error
when it comes to day of year.

-- 
Enrico Schumann
Lucerne, Switzerland
http://enricoschumann.net