{"id":667,"date":"2014-10-14T11:12:44","date_gmt":"2014-10-14T18:12:44","guid":{"rendered":"http:\/\/homepages.uc.edu\/~yaozo\/wordpress\/?p=667"},"modified":"2014-10-14T11:12:44","modified_gmt":"2014-10-14T18:12:44","slug":"how-to-convert-specific-time-format-to-timestamp-in-r","status":"publish","type":"post","link":"https:\/\/zhuoyao.net\/index.php\/2014\/10\/14\/how-to-convert-specific-time-format-to-timestamp-in-r\/","title":{"rendered":"How to convert specific time format to timestamp in R?"},"content":{"rendered":"
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This question already has an answer here:<\/p>\n

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First of all, we need to substitute the colon separating the milliseconds from the seconds to a dot, otherwise the final step won’t work (thanks to Dirk Eddelbuettel<\/a> for this one). Since in the end R will use the separators it wants, to be quicker, I’ll just go ahead and substitute all the colons for dots:<\/p>\n

x <\/span><-<\/span> \"27.05.2009 14:03:25:777\"<\/span>  # this is a simplified version of your data<\/span>\ny <\/span><-<\/span> gsub<\/span>(<\/span>\":\"<\/span>,<\/span> \".\"<\/span>,<\/span> x<\/span>)<\/span>          # this is your vector with the aforementioned substitution<\/span><\/code><\/pre>\n
By the way, this is how your vector should look after gsub<\/code>:<\/p>\n
><\/span> y\n<\/span>[<\/span>1<\/span>]<\/span> \"27.05.2009 14.03.25.777\"<\/span><\/code><\/pre>\n
Now, in order to have it show the milliseconds, you first need to adjust an R option and then use a function called strptime<\/code>, which will convert your date vector to POSIXlt (an R-friendly) format. Just do the following:<\/p>\n
><\/span> options<\/span>(<\/span>digits.secs <\/span>=<\/span> 3<\/span>)<\/span>           # this tells R you want it to consider 3 digits for seconds.<\/span>\n><\/span> strptime<\/span>(<\/span>y<\/span>,<\/span> \"%d.%m.%Y %H:%M:%OS\"<\/span>)<\/span>  # this finally formats your vector<\/span>\n[<\/span>1<\/span>]<\/span> \"2009-05-27 14:03:25.777\"<\/span><\/code><\/pre>\n
When using strptime<\/code> (or other POSIX-related functions such as as.Date<\/code>), keep in mind some of the most common conversions used (edited for brevity, as suggested by DWin<\/a>. Complete list at strptime<\/code><\/a>):<\/p>\n
I’ve learned this nice trick here<\/a>. This other answer<\/a> also says you can skip the options<\/code> setting and use, for example, strptime(y, \"%d.%m.%Y %H:%M:%OS3\")<\/code>, but it doesn’t work for me. Henrik<\/a> noted that thefunction’s help page, ?strptime<\/code><\/a> states that the %OS3<\/code> bit is OS-dependent. I’m using an updated Ubuntu 13.04 and using %OS3<\/code> yields NA<\/code>.<\/p>\n