Just a note:
If the dataset is not ordered, this could result in:
set.seed(24)
xNew<-x[sample(1:nrow(x),6,replace=FALSE),]
idxN<-which(c(TRUE,diff(as.integer(xNew[,2]))!=0))
xNew[-idxN,]
#[1] "2/1/13" "18" "30"
xNew1<-xNew[order(xNew[,2],xNew[,1]),]
idx<-which(c(TRUE,diff(as.integer(xNew1[,2]))!=0))
xNew1[-idx,]
# [,1] [,2] [,3]
#[1,] "1/5/13" "15" "25"
#[2,] "1/9/13" "15" "28"
#[3,] "2/5/13" "18" "35"
#[4,] "2/9/13" "18" "38"
#Same problem applies to my solution
xNew2<- as.data.frame(xNew, stringsAsFactors=FALSE)
xNew[with(xNew2,ave(as.numeric(as.Date(V1,"%m/%d/%y")),V2,FUN=function(x)
!x%in% min(x)))!=0,] #keeps the original order of xNew
# [,1] [,2] [,3]
#[1,] "1/5/13" "15" "25"
#[2,] "2/9/13" "18" "38"
#[3,] "1/9/13" "15" "28"
#[4,] "2/5/13" "18" "35"
A.K.
----- Original Message -----
From: Rui Barradas <ruipbarra...@sapo.pt>
To: Andras Farkas <motyoc...@yahoo.com>
Cc: "r-help@r-project.org" <r-help@r-project.org>
Sent: Tuesday, July 30, 2013 9:08 AM
Subject: Re: [R] selection based on dates
Hello,
Try the following.
idx <- which(c(TRUE, diff(as.integer(x[,2])) != 0))
x[-idx,]
Also, note that in constructs such as
a <-c("1/1/13",15,20)
both 15 and 20 are coerced to character. So your matrix is a matrix of
chars. For different types of data, use data.frames
Hope this helps,
Rui Barradas
Em 30-07-2013 13:13, Andras Farkas escreveu:
> Dear All
>
> please provide your insigths on the following:
>
> I have:
>
> a <-c("1/1/13",15,20)
> b <-c("1/5/13",15,25)
> c <-c("1/9/13",15,28)
> d <-c("2/1/13",18,30)
> e <-c("2/5/13",18,35)
> f <-c("2/9/13",18,38)
> x <-matrix(c(a,b,c,d,e,f),ncol=3,byrow=TRUE)
>
> What I would like to do is to eliminate certain rows of this matrix based on
> the date column values. As you can see, in the second column my values (15
> and 18) repeat 3 times each, so this column serves as an ID number if you
> will. Thus each ID numbers show up with 3 different date values in the first
> column. Now I would like to eliminate the rows with the earliest date per ID
> number. My result should look like this:
>
> z <-x[-c(1,4),]
>
> as allways, your help is greatly appreciated,
>
> thanks,
>
> Andras
>
> ______________________________________________
> R-help@r-project.org mailing list
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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.
>
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and provide commented, minimal, self-contained, reproducible code.
______________________________________________
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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.
