[R] readxl, read_excel: how colon (:) is read ?

[Rui Barradas]

Hello,

The following function is probably not very solid, to work with dates 
and times is not trivial, but it converts those Excel numbers correctly.

I don't know with what numbers it fails.


xl_fracday_to_time <- function(x, digits = 0L) {
   old_opts <- options(digits = 20)
   on.exit(options(old_opts))
   if(is.character(x)) {
     x <- as.numeric(x)
   }
   y <- x * 24
   hours <- floor(y + .Machine$double.eps^0.5)
   y <- (y - hours) * 60
   mins <- floor(y + .Machine$double.eps^0.5)
   y <- (y - mins) * 60
   secs <- round(y, digits = digits)
   sprintf("%02d:%02d:%02d", hours, mins, secs)
}

x <- c("0.56875000000000009", "0.57708333333333328")
xl_fracday_to_time(x)
#[1] "13:39:00" "13:51:00"


Hope this helps,

Rui Barradas

Às 07:12 de 01/04/2022, Patrick Giraudoux escreveu:
> I have a unexpected behaviour reading times with colon from an Excel
> file, using the package readxl.
> 
> In an Excel sheet, I have a column with times in hours:minutes, e.g:
> 
> Arrival_time
> 13:39
> 13:51
> 
> When read from R with readxl::read_excel, this gives a tibble column
> with full date by defaut being the last day of 1899. OK. Why not, I know
> that POSIX variables are starting in 1900 after R doc (however I wonder
> why here the defaut is one day before January 1, 1900
> 
>> tmp$Arrival_time  [1] "1899-12-31 13:39:00 UTC" "1899-12-31 13:51:00 UTC"
> 
> Well, this is not exactly what I want to. I do not care about the year
> and the day... Therefore I decided to import this column as "text"
> explicitely (in order to manage it within R then). And this is what I
> get now:
> 
>> read_excel("saisie_data_durban_rapaces_LPO.xlsx",sheet=2,col_types="text")  > tmp$Arrival_time [1] "0.56875000000000009" "0.57708333333333328"
> 
> Can someone tell me what happens ?
> 
> I would really appreciate to understand the trick...
> 
> 
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