Message-ID: <1392309402.15726.YahooMailNeo@web142605.mail.bf1.yahoo.com>
Date: 2014-02-13T16:36:42Z
From: arun
Subject: plyr: colvar value corresponding to max Date
In-Reply-To: <CAHgH9_Eo3TSxhq86uruW_YnBDMkpRuWEsbhkJMwiJ1++qDvbRg@mail.gmail.com>
Hi,
Try ?which.max() # unique values for the combination.
?ddply(data,.(state),summarize,max_date=value[which.max(date)])[,2]
#or
?ddply(data,.(state),summarize,max_date=value[date == max(date)])[,2]
A.K.
On Thursday, February 13, 2014 11:15 AM, Dan Murphy <chiefmurphy at gmail.com> wrote:
I can do this in multiple steps with summarise, joins, etc., but can't
help thinking it can be accomplished in one plyr call.
Here's a small example:
> require(plyr)
> require(lubridate)
> data <- data.frame(
+? date = rep(as.Date(ymd(20140101 + (0:3) * 100)), 2),
+? state = rep(c("A", "B"), each = 4),
+? value = rnorm(8))
What I want is clearly
> data[c(4, 8), "value"]
[1] -1.007111 -1.527541
Here are my multiple steps:
> statemaxval <- ddply(data, "state", summarise, max_date = max(date))
> rslt <- join(data, statemaxval, by = "state")
> rslt <- subset(rslt, date == max_date)
> rslt <- rslt[!duplicated(rslt), ]
> rslt$value
[1] -1.007111 -1.527541
Is there a one-step way to accomplish this?
Something like
ddply(data, "state", summarise, "GiveMeTheValueCorrespondingToMaxDateByState!!")
Or is that only possible if there is only one unique value for a given
combination of state and max(date)?
Thanks,
Dan
______________________________________________
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.