[R] Finding the two most recent dates

[jim holtman]

Here is one way of doing it:

> x
    prochi date_1st_event    bp_date SBP DBP
108  ind_1     2010-06-24 2004-08-30 135  85
109  ind_1     2010-06-24 2009-11-23 160  80
110  ind_1     2010-06-24 2006-09-01 135  NA
111  ind_1     2010-06-24 2005-10-24 153  79
112  ind_1     2010-06-24 2002-11-21 150  82
113  ind_1     2010-06-24 2005-10-24 153  79
114  ind_1     2010-06-24 2008-01-16 151  76
115  ind_1     2010-06-24 2010-01-13 126  60
116  ind_1     2010-06-24 2004-08-24 150  82
117  ind_1     2010-06-24 2008-01-16 151  91
> # find the two most recent date for an individual
> mostRecent <- lapply(split(x, x$prochi), function(.ind){
+     # get two most recent (or 1 if only one exists)
+     index <- order(.ind$bp_date, decreasing=TRUE)[1:2]
+     .ind[index,]  # return
+ })
> # put back into a dataframe
> do.call(rbind, mostRecent)
          prochi date_1st_event    bp_date SBP DBP
ind_1.115  ind_1     2010-06-24 2010-01-13 126  60
ind_1.109  ind_1     2010-06-24 2009-11-23 160  80
>


On Mon, Sep 6, 2010 at 6:45 AM, Newbie19_02 <nvanzuydam at gmail.com> wrote:
>
> Dear R help,
>
> I have the following data frame:
>
> structure(list(prochi = c("ind_1", "ind_1", "ind_1",
> "ind_1", "ind_1", "ind_1", "ind_1", "ind_1",
> "ind_1", "ind_1"), date_1st_event = structure(c(14784,
> 14784, 14784, 14784, 14784, 14784, 14784, 14784, 14784, 14784
> ), class = "Date"), bp_date = structure(c(12660, 14571, 13392,
> 13080, 12012, 13080, 13894, 14622, 12654, 13894), class = "Date"),
>    SBP = c(135L, 160L, 135L, 153L, 150L, 153L, 151L, 126L, 150L,
>    151L), DBP = c(85L, 80L, NA, 79L, 82L, 79L, 76L, 60L, 82L,
>    91L)), .Names = c("prochi", "date_1st_event", "bp_date", "SBP",
> "DBP"), row.names = 108:117, class = "data.frame")
>
> It consists of repeated measures for the same individual.  What I want to do
> is find the two most recent blood pressure readings (SBP and DBP) using
> date_1st_event and bp_date.  What I would do to find the most recent date is
> to subtract date_1st_event-bp_date and then aggregate by min.  I'm not sure
> how to find the two most recent dates.
>
> Are there some functions that can help me or will I have to write a function
> from scratch.  Any help just to point me in the right direction.
>
> Thanks,
> Natalie
> --
> View this message in context: http://r.789695.n4.nabble.com/Finding-the-two-most-recent-dates-tp2528185p2528185.html
> Sent from the R help mailing list archive at Nabble.com.
>
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>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?