Try this:
# data
DF - structure(list(id = c(1, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 4,
4, 4, 4, 4, 4, 4), date = structure(c(8, 9, 10, 11, 3, 7, 8,
10, 4, 1, 2, 3, 8, 9, 10, 11, 3, 5, 6), .Label = c(01/07/2006,
01/08/2006, 01/09/2006, 02/09/2006, 03/09/2006, 06/09/2006,
11/08/2006, 22/08/2006, 24/08/2006, 28/08/2006, 30/08/2006
), class = factor), value = c(48, 50, 150, 100, 30, 30, 100,
11, 5, 3, 100, 100, 48, 50, 150, 100, 30, 100, 100)), .Names = c(id,
date, value), class = data.frame, row.names = c(1, 2,
3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
15, 16, 17, 18, 19))
f - function(x) {
idx - which(x$value 50 c(x$value[-1], 0) 50)
if (length(idx) 0) x[idx[1],]
}
do.call(rbind, by(DF, DF$id, f))
On 8/22/06, Bonfigli Sandro [EMAIL PROTECTED] wrote:
I have a dataframe with the following structure
iddate value
-
122/08/2006 48
124/08/2006 50
128/08/2006 150
130/08/2006 100
101/09/2006 30
211/08/2006 30
222/08/2006 100
228/08/2006 11
202/09/2006 5
301/07/2006 3
301/08/2006 100
301/09/2006 100
422/08/2006 48
424/08/2006 50
428/08/2006 150
430/08/2006 100
401/09/2006 30
403/09/2006 100
406/09/2006 100
N.B.: dates in european format; ordered dataframe
For each ID I need to select the first occurrence of
all the rows which are the first of at least two with
value = 50.
Rather convoluted explication. I mean that for each id I have to select
the first row in which value is 50 only if at least the following row
has value 50 too. If this is not true I repeat the test for all the
following rows in which value 50 untill I find a record that respects
the condition
this means that with my example dataframe the result is :
iddate value
-
128/08/2006 150
301/08/2006 100
428/08/2006 150
It's clear that a for loop would work but I think that that is a better
way.
I tried by and could obtain the first row for wich value is 50.
I thought of an iterative process (delete the first row 50, find the
second row 50, examine if there are rows in the middle) but it
is quite inelegant as if the first value is not the good one I have to
repeat the process for a a priori unknown number of times.
Thanks in advance for Your help
Sandro Bonfigli
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
