[R] Selecting first and last row for each date

[arun]

Hi,
May be this helps:
dat <- read.table(text="DATE             Price
01.01.2010     2
01.01.2010     3
01.01.2010     2
01.01.2010     7
02.01.2010     3
02.01.2010     9
02.01.2010     0
03.01.2010     2
03.01.2010     4
03.01.2010     3
03.01.2010     6
03.01.2010     8",sep="",header=TRUE,stringsAsFactors=FALSE)
#If the data is ordered by "DATE"
  indx <- with(dat, DATE[-1]!=DATE[-length(DATE)]) 
dat[sort(c(which(c(TRUE,indx)),which(c(indx,TRUE)))),]

#or
library(data.table)
dt1 <- data.table(dat, key="DATE")
dt1[,list(Price=c(Price[1],Price[.N])), by="DATE"]
A.K.


Hi Everybody.

My dataset is as follows:


DATE             Price
01.01.2010     2
01.01.2010     3
01.01.2010     2
01.01.2010     7
02.01.2010     3
02.01.2010     9
02.01.2010     0
03.01.2010     2
03.01.2010     4
03.01.2010     3
03.01.2010     6
03.01.2010     8
 
I therefore have 2 columns.

I would like to extract the first and last row for each date. In other words, I would like to obtain:

DATE             Price
01.01.2010     2
01.01.2010     7
02.01.2010     3
02.01.2010     0
03.01.2010     2
03.01.2010     8

Does someone know what is the necessary code to do this?

Thank you very much !

Greetings