On 22 January 2009 at 17:39, zubin wrote: | Hello, we are receiving some data, sample below - with a weird time/date | stamp format, we need some help with R on converting this time date | stamp to a useable field in R, date and time in a data-frame. The | developer says its the number of milliseconds since midnight, January 1, | 1970. | | sample: *1232558018624* | --------------------- | | | How do I interpret the time stamp? Is there a date, i need a date and time. | site_id,survey_id,version_id,survey_start_ts,survey_question_id,start_ts,end_ts,answer | 2,registration,1,1232558018625,z1,*1232558018624*,*1232558266179*,4 | | | Answer: The timestamp is a number representing the exact date and time. | it is the number of milliseconds since midnight, January 1, 1970. Are | you using it in the DB or R? I am not sure about R's conversion of | numbers and dates. is there a way to add a number of seconds or | milliseconds to a date in R?
This is one of these cases where R excels once you understand what it does. Consider: > Sys.time() [1] "2009-01-22 23:23:42 UTC" > as.numeric(Sys.time()) [1] 1232666630 > Internal R representation is also a number (modulo maybe a factor of 1000 for your milliseconds) ! R represents time as seconds (incl. fractional parts) since Jan 1, 1970. All you need is do what help(as.POSIXct) suggests, after adjusting for milli-seconds (ie note the dot): > as.POSIXct(1232558018.624, origin="1970-01-01") [1] "2009-01-21 17:13:38 UTC" > Dirk -- Three out of two people have difficulties with fractions. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
