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Newbie19_02

2010-Sep-06 10:45 UTC

[R] Finding the two most recent dates

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
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Paul Hiemstra

2010-Sep-06 12:04 UTC

head link

[R] Finding the two most recent dates

Hi Natalie,

By far the easiest thing to do is to convert the date to a special date 
class. See as.POSIXct for example. I'm not sure that 14784 means, nor 
what the data says in the bp_date column. Probably the two combine into 
a specific date?

Once you've converted the columns into a POSIXct object, you can use the 
min() function to find the minimum.

cheers,
Paul

On 09/06/2010 12:45 PM, Newbie19_02 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
>    

-- 
Drs. Paul Hiemstra
Department of Physical Geography
Faculty of Geosciences
University of Utrecht
Heidelberglaan 2
P.O. Box 80.115
3508 TC Utrecht
Phone:  +3130 253 5773
http://intamap.geo.uu.nl/~paul
http://nl.linkedin.com/pub/paul-hiemstra/20/30b/770

Dieter Menne

2010-Sep-06 13:01 UTC

head link

[R] Finding the two most recent dates

Nathalie,

your method of sending sample data is fine. 

dt = 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")

# The most recent date
iRecent =  which.max(dt$bp_date) # index of record with most recent date
dt[iRecent,]
# ind_1     2010-06-24 2010-01-13 126  60

# To Paul Hiemstra: we have the integer representation of date here
as.integer(dt$bpdate[iRecent])

I believe that the description of your problem is not complete (homework?),
because there is only on subject and one 1st event. So please try to restate
the rest of the problem.

Dieter





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View this message in context:
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jim holtman

2010-Sep-06 13:07 UTC

head link

[R] Finding the two most recent dates

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.
>
> ______________________________________________
> R-help at 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, self-contained, reproducible code.
>


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

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