[R] Re sults sometimes in seconds with difftime unit=mins

[Ptit_Bleu]

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
> 
------------------------------------------------------------------------

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