Thank you very much. I learned a lot through your help. It worked great for the sample data. But when I try to apply the command to my dataset, I ran into two more problems.
First, the dataset is huge, it has thousands of lines. I can read it in R. Using Lines <- " data " may not work such a huge dataset. Is there a way to use data name in the commands. Second, I have two more variables, webpage and item. Using your command, I can extract data for one item (say "fans") with no problem. But under "item", there is also "views", they may have same time and date as "fans", how can I sort it out without replacing the same date? Also, under "webpage", I have two actors/actresses, it has the similar issue. How can I sort it out without replacing the same date? Thanks for the time and help. Below is the sample: > testdata <- read.csv("C:\\Users\\Kevin\\Desktop\\testdata.csv", > header=TRUE) > testdata webpage item value day date time 1 MattDamon fans 613031 Wed 10-Jun-09 9:40:53 2 MattDamon fans 630242 Thu 11-Jun-09 5:27:47 3 MattDamon fans 631966 Thu 11-Jun-09 9:23:23 4 MattDamon fans 642045 Thu 11-Jun-09 22:11:33 5 MattDamon fans 669791 Sat 13-Jun-09 13:07:53 6 MattDamon fans 700180 Mon 15-Jun-09 5:07:06 7 MattDamon fans 702949 Mon 15-Jun-09 13:09:43 8 MattDamon fans 726624 Tue 16-Jun-09 22:45:27 9 MattDamon fans 734412 Wed 17-Jun-09 13:08:19 10 MattDamon fans 765057 Fri 19-Jun-09 12:37:09 11 MattDamon fans 782741 Sat 20-Jun-09 12:38:36 12 MattDamon fans 796054 Sun 21-Jun-09 12:36:25 13 MattDamon fans 809816 Mon 22-Jun-09 12:39:36 14 MattDamon fans 833996 Tue 23-Jun-09 12:40:25 15 MattDamon fans 871237 Thu 25-Jun-09 12:38:27 16 MattDamon fans 887175 Fri 26-Jun-09 12:36:12 17 MattDamon fans 887195 Fri 26-Jun-09 13:36:12 18 MattDamon fans 899900 Sat 27-Jun-09 12:40:36 19 MattDamon fans 910401 Sun 28-Jun-09 12:38:07 20 MattDamon fans 921537 Mon 29-Jun-09 12:35:17 21 MattDamon fans 934280 Tue 30-Jun-09 12:36:43 22 MattDamon fans 986463 Mon 6-Jul-09 13:58:19 23 MattDamon views 613031 Wed 10-Jun-09 9:40:53 24 MattDamon views 630242 Thu 11-Jun-09 5:27:47 25 MattDamon views 631966 Thu 11-Jun-09 9:23:23 26 MattDamon views 642045 Thu 11-Jun-09 22:11:33 27 MattDamon views 669791 Sat 13-Jun-09 13:07:53 28 MattDamon views 700180 Mon 15-Jun-09 5:07:06 29 MattDamon views 702949 Mon 15-Jun-09 13:09:43 30 MattDamon views 726624 Tue 16-Jun-09 22:45:27 31 MattDamon views 734412 Wed 17-Jun-09 13:08:19 32 MattDamon views 765057 Fri 19-Jun-09 12:37:09 33 MattDamon views 782741 Sat 20-Jun-09 12:38:36 34 MattDamon views 796054 Sun 21-Jun-09 12:36:25 35 MattDamon views 809816 Mon 22-Jun-09 12:39:36 36 MattDamon views 833996 Tue 23-Jun-09 12:40:25 37 MattDamon views 871237 Thu 25-Jun-09 12:38:27 38 MattDamon views 887175 Fri 26-Jun-09 12:36:12 39 MattDamon views 887195 Fri 26-Jun-09 13:36:12 40 MattDamon views 899900 Sat 27-Jun-09 12:40:36 41 MattDamon views 910401 Sun 28-Jun-09 12:38:07 42 MattDamon views 921537 Mon 29-Jun-09 12:35:17 43 MattDamon views 934280 Tue 30-Jun-09 12:36:43 44 MattDamon views 986463 Mon 6-Jul-09 13:58:19 45 AngelinaJolie fans 613031 Wed 10-Jun-09 9:40:53 46 AngelinaJolie fans 630242 Thu 11-Jun-09 5:27:47 47 AngelinaJolie fans 631966 Thu 11-Jun-09 9:23:23 48 AngelinaJolie fans 642045 Thu 11-Jun-09 22:11:33 49 AngelinaJolie fans 669791 Sat 13-Jun-09 13:07:53 50 AngelinaJolie fans 700180 Mon 15-Jun-09 5:07:06 51 AngelinaJolie fans 702949 Mon 15-Jun-09 13:09:43 52 AngelinaJolie fans 726624 Tue 16-Jun-09 22:45:27 53 AngelinaJolie fans 734412 Wed 17-Jun-09 13:08:19 54 AngelinaJolie fans 765057 Fri 19-Jun-09 12:37:09 55 AngelinaJolie fans 782741 Sat 20-Jun-09 12:38:36 56 AngelinaJolie fans 796054 Sun 21-Jun-09 12:36:25 57 AngelinaJolie fans 809816 Mon 22-Jun-09 12:39:36 58 AngelinaJolie fans 833996 Tue 23-Jun-09 12:40:25 59 AngelinaJolie fans 871237 Thu 25-Jun-09 12:38:27 60 AngelinaJolie fans 887175 Fri 26-Jun-09 12:36:12 61 AngelinaJolie fans 887195 Fri 26-Jun-09 13:36:12 62 AngelinaJolie fans 899900 Sat 27-Jun-09 12:40:36 63 AngelinaJolie fans 910401 Sun 28-Jun-09 12:38:07 64 AngelinaJolie fans 921537 Mon 29-Jun-09 12:35:17 65 AngelinaJolie fans 934280 Tue 30-Jun-09 12:36:43 66 AngelinaJolie fans 986463 Mon 6-Jul-09 13:58:19 67 AngelinaJolie views 613031 Wed 10-Jun-09 9:40:53 68 AngelinaJolie views 630242 Thu 11-Jun-09 5:27:47 69 AngelinaJolie views 631966 Thu 11-Jun-09 9:23:23 70 AngelinaJolie views 642045 Thu 11-Jun-09 22:11:33 71 AngelinaJolie views 669791 Sat 13-Jun-09 13:07:53 72 AngelinaJolie views 700180 Mon 15-Jun-09 5:07:06 73 AngelinaJolie views 702949 Mon 15-Jun-09 13:09:43 74 AngelinaJolie views 726624 Tue 16-Jun-09 22:45:27 75 AngelinaJolie views 734412 Wed 17-Jun-09 13:08:19 76 AngelinaJolie views 765057 Fri 19-Jun-09 12:37:09 77 AngelinaJolie views 782741 Sat 20-Jun-09 12:38:36 78 AngelinaJolie views 796054 Sun 21-Jun-09 12:36:25 79 AngelinaJolie views 809816 Mon 22-Jun-09 12:39:36 80 AngelinaJolie views 833996 Tue 23-Jun-09 12:40:25 81 AngelinaJolie views 871237 Thu 25-Jun-09 12:38:27 82 AngelinaJolie views 887175 Fri 26-Jun-09 12:36:12 83 AngelinaJolie views 887195 Fri 26-Jun-09 13:36:12 84 AngelinaJolie views 899900 Sat 27-Jun-09 12:40:36 85 AngelinaJolie views 910401 Sun 28-Jun-09 12:38:07 86 AngelinaJolie views 921537 Mon 29-Jun-09 12:35:17 87 AngelinaJolie views 934280 Tue 30-Jun-09 12:36:43 88 AngelinaJolie views 986463 Mon 6-Jul-09 13:58:19 -- View this message in context: http://r.789695.n4.nabble.com/How-to-extract-Friday-data-from-daily-data-tp3029050p3030555.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ R-help@r-project.org 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, 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