[R] How to extract Friday data from daily data.

[thornbird]

I did the following but it shows a couple of error messages. Could you help
me with that? Thanks in advance. 



> testdata <- read.csv("C:\\Users\\Kevin\\Desktop\\testdata.csv",
> header=TRUE)
> testdata
        date day     time     webpage  item  value
1  10-Jun-09 Wed  9:40:53   MattDamon  fans 613031
2  11-Jun-09 Thu  5:27:47   MattDamon  fans 630242
3  11-Jun-09 Thu  9:23:23   MattDamon  fans 631966
4  11-Jun-09 Thu 22:11:33   MattDamon  fans 642045
5  13-Jun-09 Sat 13:07:53   MattDamon  fans 669791
6  15-Jun-09 Mon  5:07:06   MattDamon  fans 700180
7  15-Jun-09 Mon 13:09:43   MattDamon  fans 702949
8  16-Jun-09 Tue 22:45:27   MattDamon  fans 726624
9  17-Jun-09 Wed 13:08:19   MattDamon  fans 734412
10 19-Jun-09 Fri 12:37:09   MattDamon  fans 765057
11 20-Jun-09 Sat 12:38:36   MattDamon  fans 782741
12 21-Jun-09 Sun 12:36:25   MattDamon  fans 796054
13 22-Jun-09 Mon 12:39:36   MattDamon  fans 809816
14 23-Jun-09 Tue 12:40:25   MattDamon  fans 833996
15 27-Jun-09 Sat 12:40:36   MattDamon  fans 899900
16 28-Jun-09 Sun 12:38:07   MattDamon  fans 910401
17 10-Jun-09 Wed  9:40:53   MattDamon views 613031
18 11-Jun-09 Thu  5:27:47   MattDamon views 630242
19 11-Jun-09 Thu  9:23:23   MattDamon views 631966
20 11-Jun-09 Thu 22:11:33   MattDamon views 642045
21 13-Jun-09 Sat 13:07:53   MattDamon views 669791
22 15-Jun-09 Mon  5:07:06   MattDamon views 700180
23 15-Jun-09 Mon 13:09:43   MattDamon views 702949
24 16-Jun-09 Tue 22:45:27   MattDamon views 726624
25 17-Jun-09 Wed 13:08:19   MattDamon views 734412
26 19-Jun-09 Fri 12:37:09   MattDamon views 765057
27 20-Jun-09 Sat 12:38:36   MattDamon views 782741
28 21-Jun-09 Sun 12:36:25   MattDamon views 796054
29 22-Jun-09 Mon 12:39:36   MattDamon views 809816
30 23-Jun-09 Tue 12:40:25   MattDamon views 833996
31 25-Jun-09 Thu 12:38:27   MattDamon views 871237
32 26-Jun-09 Fri 12:36:12   MattDamon views 887175
33 26-Jun-09 Fri 13:36:12   MattDamon views 887195
34 27-Jun-09 Sat 12:40:36   MattDamon views 899900
35 10-Jun-09 Wed  9:40:53 AngieeJolie  fans 613031
36 11-Jun-09 Thu  5:27:47 AngieeJolie  fans 630242
37 11-Jun-09 Thu  9:23:23 AngieeJolie  fans 631966
38 11-Jun-09 Thu 22:11:33 AngieeJolie  fans 642045
39 13-Jun-09 Sat 13:07:53 AngieeJolie  fans 669791
40 15-Jun-09 Mon  5:07:06 AngieeJolie  fans 700180
41 16-Jun-09 Tue 22:45:27 AngieeJolie  fans 726624
42 17-Jun-09 Wed 13:08:19 AngieeJolie  fans 734412
43 19-Jun-09 Fri 12:37:09 AngieeJolie  fans 765057
44 20-Jun-09 Sat 12:38:36 AngieeJolie  fans 782741
45 21-Jun-09 Sun 12:36:25 AngieeJolie  fans 796054
46 22-Jun-09 Mon 12:39:36 AngieeJolie  fans 809816
47 23-Jun-09 Tue 12:40:25 AngieeJolie  fans 833996
48 25-Jun-09 Thu 12:38:27 AngieeJolie  fans 871237
49 26-Jun-09 Fri 12:36:12 AngieeJolie  fans 887175
50 26-Jun-09 Fri 13:36:12 AngieeJolie  fans 887195
51 30-Jun-09 Tue 12:36:43 AngieeJolie  fans 934280
52 10-Jun-09 Wed  9:40:53 AngieeJolie views 613031
53 11-Jun-09 Thu  5:27:47 AngieeJolie views 630242
54 11-Jun-09 Thu  9:23:23 AngieeJolie views 631966
55 11-Jun-09 Thu 22:11:33 AngieeJolie views 642045
56 13-Jun-09 Sat 13:07:53 AngieeJolie views 669791
57 15-Jun-09 Mon  5:07:06 AngieeJolie views 700180
58 15-Jun-09 Mon 13:09:43 AngieeJolie views 702949
59 16-Jun-09 Tue 22:45:27 AngieeJolie views 726624
60 17-Jun-09 Wed 13:08:19 AngieeJolie views 734412
61 19-Jun-09 Fri 12:37:09 AngieeJolie views 765057
62 20-Jun-09 Sat 12:38:36 AngieeJolie views 782741
63 21-Jun-09 Sun 12:36:25 AngieeJolie views 796054
64 22-Jun-09 Mon 12:39:36 AngieeJolie views 809816
65 23-Jun-09 Tue 12:40:25 AngieeJolie views 833996
66 25-Jun-09 Thu 12:38:27 AngieeJolie views 871237
67 26-Jun-09 Fri 12:36:12 AngieeJolie views 887175
68 26-Jun-09 Fri 13:36:12 AngieeJolie views 887195
69 27-Jun-09 Sat 12:40:36 AngieeJolie views 899900
> 
> library(zoo)
> 
> colClasses <- c("character", "character", "numeric", "character",
> "character", "numeric")
> 
> col.names <- c("date", "day", "time", "webpage", "item", "value")
> 
> # z <- read.zoo("myfile.dat", skip = 1, index = as.list(1:5),
> z <- read.zoo(testdata[,1:5],as.Date(as.character(testdata[, 1])),skip =
> 1, index = as.list(1:6),
+         format = "%d/%m/%Y", col.names = col.names,
+         aggregate = function(x) tail(x, 1), colClasses = colClasses)
Error in `[.data.frame`(rval, , j) : undefined columns selected
> 
> ## Now that we have read it in lets process it
> 
> ## 1.
> 
> # extract all Thursdays and Fridays
> z45 <- z[format(time(z), "%w") %in% 4:5,]
Error: object 'z' not found
> 
> # keep last entry in each week
> # and show result on R console
> z45[!duplicated(format(time(z45), "%U"), fromLast = TRUE), ]
Error: object 'z45' not found

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