I think the problem is is that 'diff' does not have a 'units' parameter; 'difftime' does. Here is a way of doing it:
> x [1] "2009-03-27 13:00:00 EDT" "2009-03-27 13:00:35 EDT" "2009-03-27 13:01:10 EDT" "2009-03-27 13:01:45 EDT" "2009-03-27 13:02:20 EDT" "2009-03-27 13:02:55 EDT" "2009-03-27 13:03:30 EDT" [8] "2009-03-27 13:04:05 EDT" "2009-03-27 13:04:40 EDT" "2009-03-27 13:05:15 EDT" > difftime(tail(x, -1), head(x, -1), units='mins') Time differences in mins [1] 0.5833333 0.5833333 0.5833333 0.5833333 0.5833333 0.5833333 0.5833333 0.5833333 0.5833333 attr(,"tzone") [1] "" > diff(x, units='mins') # 'units' ignored Time differences in secs [1] 35 35 35 35 35 35 35 35 35 attr(,"tzone") [1] "" > On Fri, Mar 27, 2009 at 11:04 AM, Ptit_Bleu <[email protected]> wrote: > > Hello, > > I'm trying to calculate an integration and x-axis is a time (format : > %Y-%m-%d %H:%M:%S"). > I use diff(date, units="mins") in a loop for but sometimes the results stay > in seconds (95% is ok). > > Examples for 2 sets of data are given below (first result stays in seconds > whereas the second in minutes as expected). > Have you already seen this behaviour ? > Any idea to solve this problem ? > > Thanks in advance. > Have a good week-end, > Ptit Bleu. > > ------------------------------------------------------------------------ >> strptime(datajour$Date, format="%Y-%m-%d %H:%M:%S") > [1] "2009-03-26 11:21:31" "2009-03-26 11:22:17" "2009-03-26 11:27:18" > "2009-03-26 11:36:59" "2009-03-26 11:41:59" "2009-03-26 11:46:59" > [7] "2009-03-26 11:51:59" "2009-03-26 11:57:00" "2009-03-26 12:02:00" > "2009-03-26 12:07:00" "2009-03-26 12:12:00" "2009-03-26 12:17:00" > [13] "2009-03-26 12:22:00" "2009-03-26 12:27:01" "2009-03-26 12:32:01" > "2009-03-26 12:37:01" "2009-03-26 12:42:01" "2009-03-26 12:47:01" > [19] "2009-03-26 12:52:01" "2009-03-26 12:57:01" "2009-03-26 13:02:02" > "2009-03-26 13:07:02" "2009-03-26 13:12:03" "2009-03-26 13:17:03" > [25] "2009-03-26 13:22:03" "2009-03-26 13:27:03" "2009-03-26 13:32:03" > "2009-03-26 13:37:03" "2009-03-26 13:42:03" "2009-03-26 13:47:03" > [31] "2009-03-26 13:52:03" "2009-03-26 13:57:04" "2009-03-26 14:01:02" > "2009-03-26 14:06:05" "2009-03-26 14:11:05" "2009-03-26 14:16:06" > [37] "2009-03-26 14:21:06" "2009-03-26 14:26:08" "2009-03-26 14:31:09" > "2009-03-26 14:36:10" "2009-03-26 14:41:10" "2009-03-26 14:46:15" > [43] "2009-03-26 14:51:15" "2009-03-26 14:56:15" "2009-03-26 15:01:15" > "2009-03-26 15:06:17" "2009-03-26 15:11:17" "2009-03-26 15:16:19" > [49] "2009-03-26 15:21:19" "2009-03-26 15:26:19" "2009-03-26 15:31:22" > "2009-03-26 15:36:23" "2009-03-26 15:41:24" "2009-03-26 15:46:24" > [55] "2009-03-26 15:51:25" "2009-03-26 15:56:25" "2009-03-26 16:01:25" > "2009-03-26 16:06:26" "2009-03-26 16:11:26" "2009-03-26 16:16:26" > [61] "2009-03-26 16:21:27" "2009-03-26 16:26:27" "2009-03-26 16:31:28" > "2009-03-26 16:36:28" "2009-03-26 16:41:29" "2009-03-26 16:46:30" > [67] "2009-03-26 16:51:31" "2009-03-26 16:56:31" "2009-03-26 17:01:32" > "2009-03-26 17:06:32" "2009-03-26 17:11:33" "2009-03-26 17:16:33" > [73] "2009-03-26 17:21:33" "2009-03-26 17:26:35" "2009-03-26 17:31:36" > "2009-03-26 17:36:36" "2009-03-26 17:41:36" "2009-03-26 17:46:36" > [79] "2009-03-26 17:51:39" "2009-03-26 17:56:40" "2009-03-26 18:01:40" > "2009-03-26 18:06:40" "2009-03-26 18:11:40" "2009-03-26 18:16:40" > [85] "2009-03-26 18:21:41" "2009-03-26 18:26:41" "2009-03-26 18:31:41" > "2009-03-26 18:36:41" "2009-03-26 18:41:41" "2009-03-26 18:46:41" > [91] "2009-03-26 18:51:42" "2009-03-26 18:56:42" "2009-03-26 19:06:42" >> >> as.numeric(diff(strptime(datajour$Date, format="%Y-%m-%d %H:%M:%S"), >> units="mins")) > [1] 46 301 581 300 300 300 301 300 300 300 300 300 301 300 300 300 300 300 > 300 301 300 301 300 300 300 300 300 300 300 300 301 238 303 300 301 300 302 > 301 > [39] 301 300 305 300 300 300 302 300 302 300 300 303 301 301 300 301 300 300 > 301 300 300 301 300 301 300 301 301 301 300 301 300 301 300 300 302 301 300 > 300 > [77] 300 303 301 300 300 300 300 301 300 300 300 300 300 301 300 600 > > ------------------------------------------------------------------------ >> strptime(datajour$Date, format="%Y-%m-%d %H:%M:%S") > [1] "2009-03-26 11:22:24" "2009-03-26 11:27:25" "2009-03-26 11:37:04" > "2009-03-26 11:42:04" "2009-03-26 11:47:04" "2009-03-26 11:52:04" > [7] "2009-03-26 11:57:04" "2009-03-26 12:02:05" "2009-03-26 12:07:06" > "2009-03-26 12:12:06" "2009-03-26 12:17:06" "2009-03-26 12:22:06" > [13] "2009-03-26 12:27:07" "2009-03-26 12:32:07" "2009-03-26 12:37:07" > "2009-03-26 12:42:07" "2009-03-26 12:47:07" "2009-03-26 12:52:08" > [19] "2009-03-26 12:57:08" "2009-03-26 13:02:08" "2009-03-26 13:07:09" > "2009-03-26 13:12:09" "2009-03-26 13:17:09" "2009-03-26 13:22:09" > [25] "2009-03-26 13:27:09" "2009-03-26 13:32:09" "2009-03-26 13:37:09" > "2009-03-26 13:42:09" "2009-03-26 13:47:09" "2009-03-26 13:52:09" > [31] "2009-03-26 13:57:10" "2009-03-26 14:01:08" "2009-03-26 14:06:11" > "2009-03-26 14:11:11" "2009-03-26 14:16:12" "2009-03-26 14:21:12" > [37] "2009-03-26 14:26:15" "2009-03-26 14:31:18" "2009-03-26 14:36:18" > "2009-03-26 14:41:19" "2009-03-26 14:46:22" "2009-03-26 14:51:22" > [43] "2009-03-26 14:56:23" "2009-03-26 15:01:24" "2009-03-26 15:06:24" > "2009-03-26 15:11:24" "2009-03-26 15:16:24" "2009-03-26 15:21:24" > [49] "2009-03-26 15:26:24" "2009-03-26 15:31:28" "2009-03-26 15:36:29" > "2009-03-26 15:41:29" "2009-03-26 15:46:30" "2009-03-26 15:51:33" > [55] "2009-03-26 15:56:33" "2009-03-26 16:01:33" "2009-03-26 16:06:33" > "2009-03-26 16:11:34" "2009-03-26 16:16:34" "2009-03-26 16:21:35" > [61] "2009-03-26 16:26:35" "2009-03-26 16:31:35" "2009-03-26 16:36:35" > "2009-03-26 16:41:35" "2009-03-26 16:46:36" "2009-03-26 16:51:37" > [67] "2009-03-26 16:56:37" "2009-03-26 17:01:37" "2009-03-26 17:06:38" > "2009-03-26 17:11:38" "2009-03-26 17:16:38" "2009-03-26 17:21:38" > [73] "2009-03-26 17:26:40" "2009-03-26 17:31:43" "2009-03-26 17:36:43" > "2009-03-26 17:41:43" "2009-03-26 17:46:44" "2009-03-26 17:51:45" > [79] "2009-03-26 17:56:46" "2009-03-26 18:01:46" "2009-03-26 18:06:46" > "2009-03-26 18:11:47" "2009-03-26 18:16:47" "2009-03-26 18:21:48" > [85] "2009-03-26 18:26:48" "2009-03-26 18:31:48" "2009-03-26 18:36:48" > "2009-03-26 18:41:48" "2009-03-26 18:46:48" "2009-03-26 18:51:48" > [91] "2009-03-26 18:56:48" "2009-03-26 19:01:48" >> >> as.numeric(diff(strptime(datajour$Date, format="%Y-%m-%d %H:%M:%S"), >> units="mins")) > [1] 5.016667 9.650000 5.000000 5.000000 5.000000 5.000000 5.016667 5.016667 > 5.000000 5.000000 5.000000 5.016667 5.000000 5.000000 5.000000 5.000000 > [17] 5.016667 5.000000 5.000000 5.016667 5.000000 5.000000 5.000000 5.000000 > 5.000000 5.000000 5.000000 5.000000 5.000000 5.016667 3.966667 5.050000 > [33] 5.000000 5.016667 5.000000 5.050000 5.050000 5.000000 5.016667 5.050000 > 5.000000 5.016667 5.016667 5.000000 5.000000 5.000000 5.000000 5.000000 > [49] 5.066667 5.016667 5.000000 5.016667 5.050000 5.000000 5.000000 5.000000 > 5.016667 5.000000 5.016667 5.000000 5.000000 5.000000 5.000000 5.016667 > [65] 5.016667 5.000000 5.000000 5.016667 5.000000 5.000000 5.000000 5.033333 > 5.050000 5.000000 5.000000 5.016667 5.016667 5.016667 5.000000 5.000000 > [81] 5.016667 5.000000 5.016667 5.000000 5.000000 5.000000 5.000000 5.000000 > 5.000000 5.000000 5.000000 >> > ------------------------------------------------------------------------ > > -- > View this message in context: > http://www.nabble.com/Results-sometimes-in-seconds-with-difftime-unit%3Dmins-tp22743564p22743564.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > [email protected] 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. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve? ______________________________________________ [email protected] 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.
