Calculate time difference in R - r

Question

I'm currently struggling with R and calculating the time difference in days.
I have data.frame with around 60 000 rows. In this data frame there are two columns called "start" and "end". Both columns contain data in UNIX time format WITH milliseconds - as you can see by the last three digits.
Start <- c("1470581434000", "1470784954000", "1470811368000", "1470764345000")
End <- c("1470560601000", "1470581549000", "1470785452000", "1470764722000")
d <- data.frame(Start, End)
My desired output should be a extra column called timediff where the time difference is outline in days.
I tried it with timediff and strptime which I found here. But nothing worked out.
Maybe one of you worked with calculation of time differences in the past.
Thanks a lot

Answer 1

There is a very small and fast solution:
Start_POSIX <- as.POSIXct(as.numeric(Start)/1000, origin="1970-01-01")
End_POSIX <- as.POSIXct(as.numeric(End)/1000, origin="1970-01-01")
difftime(Start_POSIX, End_POSIX)
Time differences in mins
[1] 347.216667 3390.083333 431.933333 -6.283333
or if you want another unit:
difftime(Start_POSIX, End_POSIX, unit = "sec")
Time differences in secs
[1] 20833 203405 25916 -377

Answer 2

You have a few steps you'll need to take:
# 1. Separate the milliseconds.
# To do this, insert a period in front of the last three digits
Start <-
sub(pattern = "(\\d{3}$)", # get the pattern of three digits at the end of the string
replacement = ".\\1", # replace with a . and then the pattern
x = Start)
# 2. Convert to numeric
Start <- as.numeric(Start)
# 3. Convert to POSIXct
Start <- as.POSIXct(Start,
origin = "1970-01-01")
For convenience, it would be good to put these all into a function
# Bundle all three steps into one function
unixtime_to_posixct <- function(x)
{
x <- sub(pattern = "(\\d{3}$)",
replacement = ".\\1",
x = x)
x <- as.numeric(x)
as.POSIXct(x,
origin = "1970-01-01")
}
And with that, you can get your differences in days
#* Put it all together.
library(dplyr)
library(magrittr)
Start <- c("1470581434000", "1470784954000", "1470811368000", "1470764345000")
End <- c("1470560601000", "1470581549000", "1470785452000", "1470764722000")
d <- data.frame(Start,
End,
stringsAsFactors = FALSE)
lapply(
X = d,
FUN = unixtime_to_posixct
) %>%
as.data.frame() %>%
mutate(diff = difftime(Start, End, units = "days"))