If I understand your question, you can try this: data$M1date <- as.Date(strptime(data$M1date, "%m/%d/%Y")) data$M2date <- as.Date(strptime(data$M2date, "%m/%d/%Y")) data$Days <- data$M2date - data$M1date
On 07/02/2008, Tom Cohen <[EMAIL PROTECTED]> wrote: > Dear list, > > I have two data columns (part of big data frame) containing dates presenting > the dates when > two measurements (M1 and M2) were taken. The data consists of 73 individuals > divided > in different groups. Each group was examined at different time points (see M1 > date),but > the measurements (M1 and M2) within each group should be taken in the same > day but due > to some practical issues, some M2-measurents were taken on another day. All > individuals > measured at the same day in column M1date belong to one group. > For example, 24 measurements were taken 8/15/2005 (M1date column,one group of > individual) > but only 4 M2-mesurements were taken at the same day, the 24-2=20 > M2-measurements were > taken 2-65 days later within this group. > For analysis, I need to know how many days the M2-measurements were taken if > they were not taken at the same day as M1-measurements within each group. > Each of the > different dates in column M1date would reflect the starting date for each > group,for example > 8/15/2005 is starting date for one group, and 8/8/2005 is a starting date for > another group, so if > M2-measurements wíthin group were taken for example 8/15/2005, then we say > that > they were taken at day 1, and if they were taken 8/16/2005 we say they were > taken > 2 days after the starting date for that group and so on. For group with > starting date > 8/8/2005, if the M2-measurements were taken at the same date, then these > would be considered > taken at day 1 and for those that were taken 8/9/2005, we say they were > taken at day 2 for this group > In the below data, I have manually calculated the number of days when > M2-measurements > were taken if they were not taken at > the starting day for some individuals (column Days). Is there any automatic > ways to do this in R ? > > M1date M2date Days > 75 8/15/2005 8/15/2005 1 > 79 8/15/2005 8/16/2005 2 > 76 8/15/2005 8/15/2005 1 > 84 8/15/2005 8/16/2005 2 > 74 8/15/2005 8/15/2005 1 > 80 8/15/2005 8/16/2005 2 > 77 8/15/2005 8/15/2005 1 > 81 8/15/2005 8/16/2005 2 > 82 8/15/2005 8/16/2005 2 > 78 8/15/2005 8/16/2005 2 > 83 8/15/2005 8/16/2005 2 > 85 8/15/2005 10/17/2005 62 > 2 8/15/2005 10/19/2005 64 > 1 8/15/2005 10/18/2005 63 > 5 8/16/2005 10/19/2005 65 > 3 8/15/2005 10/19/2005 65 > 4 8/15/2005 10/19/2005 65 > 6 8/15/2005 10/19/2005 65 > 12 8/8/2005 8/9/2005 2 > 10 8/8/2005 8/9/2005 2 > 11 8/8/2005 8/9/2005 2 > 8 8/8/2005 11/7/2005 > 7 8/8/2005 11/8/2005 > 9 8/8/2005 8/8/2005 > 29 8/8/2005 11/10/2005 > 25 8/8/2005 11/9/2005 > 30 8/8/2005 11/10/2005 > 28 8/8/2005 11/9/2005 > 32 8/15/2005 11/10/2005 > 33 8/15/2005 11/10/2005 > 31 8/15/2005 11/10/2005 > 24 8/15/2005 11/9/2005 > 26 8/15/2005 11/9/2005 > 27 8/15/2005 11/9/2005 > 14 7/31/2006 11/15/2006 > 18 7/31/2006 11/13/2006 > 13 7/31/2006 11/15/2006 > 16 7/31/2006 11/16/2006 > 20 7/31/2006 11/14/2006 > 17 7/31/2006 11/16/2006 > 19 7/31/2006 11/13/2006 > 37 8/7/2006 8/7/2006 > 39 8/7/2006 8/7/2006 > 42 8/7/2006 9/20/2006 > 49 8/7/2006 9/21/2006 > 52 8/7/2006 9/21/2006 > 50 8/7/2006 9/21/2006 > 47 8/7/2006 9/21/2006 > 38 8/7/2006 8/7/2006 > 45 8/7/2006 9/19/2006 > 43 8/7/2006 9/20/2006 > 48 8/7/2006 9/21/2006 > 36 8/7/2006 8/7/2006 > 44 8/7/2006 9/20/2006 > 46 8/7/2006 9/19/2006 > 51 8/7/2006 9/21/2006 > 41 8/7/2006 8/8/2006 > 40 8/7/2006 8/8/2006 > 68 7/31/2006 9/28/2006 > 59 7/31/2006 8/1/2006 > 69 7/31/2006 9/28/2006 > 71 7/31/2006 9/28/2006 > 58 8/1/2006 9/27/2006 > 60 7/31/2006 8/1/2006 > 70 7/31/2006 9/28/2006 > 66 7/31/2006 9/28/2006 > 67 7/31/2006 9/28/2006 > 72 7/31/2006 9/28/2006 > 64 8/1/2006 8/1/2006 > 61 7/31/2006 8/1/2006 > 62 7/31/2006 8/1/2006 > 63 7/31/2006 8/1/2006 > 65 7/31/2006 8/1/2006 > > Thanks for any help, > Tom > > > > --------------------------------- > Går det långsamt? Skaffa dig en snabbare bredbandsuppkoppling. > > [[alternative HTML version deleted]] > > > ______________________________________________ > [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. > > -- Henrique Dallazuanna Curitiba-Paraná-Brasil 25° 25' 40" S 49° 16' 22" O ______________________________________________ [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.
