I am trying to follow the instructions in another StackOverflow post because I have a similar problem: I need to convert a timestamp to days (or hours) after an event.
My issue is that I keep getting this error when I try to convert my timestamp to date:
Error in assign(cacheKey, frame, .rs.CachedDataEnv) : attempt to use zero-length variable name
Supposedly this means that I'm including the separators in the code, but I'm not sure what this means in the context of this specific dataset or how to address it.
This should be a reproducible example:
sample <- c(1,2,3,4,5)
timestamp <- c('2023-07-17-15-05','2023-07-17-16-05','2023-07-17-17-05','2023-07-18-15-05','2023-07-17-19-05')
area <- c(255,345,200,177,189)
df <- data.frame(sample,timestamp,area)
df$timestamp <- as.Date(df$timestamp,format='%Y-%m-%d_%h-%m')
The timestamp layout is year-month-day-hour-minute, if that helps.
This happens whether there are dashes or slashes in the code. I'm not 100% sure if that underscore is the proper way to separate hours and minutes, but it still throws the same error if I use:
sample <- c(1,2,3,4,5)
timestamp <- c('2023-07-17-15-05','2023-07-17-16-05','2023-07-17-17-05','2023-07-18-15-05','2023-07-17-19-05')
area <- c(255,345,200,177,189)
df <- data.frame(sample,timestamp,area)
df$timestamp <- as.Date(df$timestamp,format='%Y-%m-%d-%h-%m')
I've tried googling the error, but cannot find any explanations which make sense to me as to what's going on with this specific timestamp or anything which points to a fix.
Thanks in advance!
Using timestamp in the Note at the end, if you are trying to convert it to a date with no hours and minutes then these work. See ?strptime for info on the percent codes.
as.Date(timestamp) # as.Date ignores junk at end
## [1] "2023-07-17" "2023-07-17" "2023-07-17" "2023-07-18" "2023-07-17"
as.Date(timestamp, "%Y-%m-%d") # only need year, month & day in format
## [1] "2023-07-17" "2023-07-17" "2023-07-17" "2023-07-18" "2023-07-17"
as.Date(timestamp, "%F") # same as %Y-%m-%d
## [1] "2023-07-17" "2023-07-17" "2023-07-17" "2023-07-18" "2023-07-17"
or if you are trying to keep the hours and minutes then be sure the format corresponds to the input. The input has a - after the day, not an underscore, so the following works. Unless you really need hours and minutes it is better to use just the date as above since date and time involve time zones which can result in subtle errors and fragile code. See ?DateTimeClasses and ?as.POSIXct for more info.
as.POSIXct(timestamp, format = "%Y-%m-%d-%H-%M")
## [1] "2023-07-17 15:05:00 EDT" "2023-07-17 16:05:00 EDT"
## [3] "2023-07-17 17:05:00 EDT" "2023-07-18 15:05:00 EDT"
## [5] "2023-07-17 19:05:00 EDT"
as.POSIXct(timestamp, format = "%F-%H-%M") # same
## [1] "2023-07-17 15:05:00 EDT" "2023-07-17 16:05:00 EDT"
## [3] "2023-07-17 17:05:00 EDT" "2023-07-18 15:05:00 EDT"
## [5] "2023-07-17 19:05:00 EDT"
lubridate::ymd_hm(timestamp) # UTC time zone rather than local
## [1] "2023-07-17 15:05:00 UTC" "2023-07-17 16:05:00 UTC"
## [3] "2023-07-17 17:05:00 UTC" "2023-07-18 15:05:00 UTC"
## [5] "2023-07-17 19:05:00 UTC"
timestamp <- c('2023-07-17-15-05','2023-07-17-16-05',
'2023-07-17-17-05','2023-07-18-15-05','2023-07-17-19-05')