[R] order a data frame by date with order

[Benedikt Gehr]

Hi

I have a rather large data frame (>7000 rows with 28 columns) which I want
to sort by date. Below I have a example of the data frame. The Date column
is called DT, is a factor and looks like this:

class(res.merge$DT)
[1] "factor"
head(res.merge$DT)
[1] 17.3.2012 13:54:02 17.3.2012 14:00:07 17.3.2012 14:30:25 17.3.2012
15:01:15
[5] 17.3.2012 15:32:14 17.3.2012 16:01:29
2530 Levels: 1.4.2012 00:00:52 1.4.2012 00:30:29 ... 9.5.2012 15:30:50

res.merge is the data frame unordered. Now I want to order the data frame
with:

res.ordered<-res.merge[order(as.POSIXct(as.character(res.merge$DT),format="%d.%m.%Y
%H:%M:%S")),]

This works in fact, however for some reason there are always two entires
that go at the end of the data frame for no obvious reason (see below,
09.05.2012 ist the most recent date). And this is the case for different
data.frames. The two entries at the end are always 25.3.2012 02:00:xx and
25.3.2012 02.30.xx.

Can anybody tell me what the problem is? Any help is most appreciated.

Best Benedikt

res.ordered[2545:2549,]
                     DT Typ  NOD     Day_s DOW_s   Time_s     Long      Lat
2547  9.5.2012 14:30:56 GPS 1893  9.5.2012    We 14:30:00 7.452218 46.43579
2548  9.5.2012 15:02:09 GPS 1893  9.5.2012    We 15:00:35 7.451983 46.43583
2549  9.5.2012 15:30:50 GPS 1893  9.5.2012    We 15:30:00 7.451973 46.43597
1845 25.3.2012 02:00:18 GPS 1848 25.3.2012    So 02:00:01 7.454266 46.45414
1846 25.3.2012 02:30:16 GPS 1848 25.3.2012    So 02:30:00 7.454413 46.45437
     Height TOF Status FO_GPS GPS_N AOT     Day_e DOW_e   Time_e   BV Temp 
SOG
2547 1182.8   3      A      1   143  55  9.5.2012    We 14:30:56 3735   31
0.09
2548 1182.8   3      A      1   143  94  9.5.2012    We 15:02:09 3637   32
0.02
2549 1176.5   3      A      1   143  50  9.5.2012    We 15:30:50 3730   29
0.17
1845 1295.2   3      A      1   151  17 25.3.2012    So 02:00:18 3715    7
0.18
1846 1287.3   3      A      1   144  16 25.3.2012    So 02:30:16 3720    8
0.14
     Heading  SAE  HAE BW_2 BW_3  X..
2547   24.90 3.81 9.47 3666 3625 9.08
2548    7.86 0.51 7.17 3593 3586 9.11
2549  344.72 2.86 4.10 3662 3623 9.12
1845  335.54 3.53 5.63 3618 3618 0.81
1846   75.37 5.44 8.96 3618 3618 0.81

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