Hi. Yes it is possible.
Here is one approach:
DF <- read.table(textConnection("
Unit Day Hour Price Flag
afd1 1/2/2003 1 1 N
afd1 1/2/2003 1 2 N
afd1 1/2/2003 1 3 N
afd1 1/2/2003 1 4 Y
dcf1 1/2/2003 2 2 N
dcf1 1/2/2003 2 3 Y
dcf1 1/2/2003 2 1 N
dcf1 1/2/2003 2 2 N
dcf1 1/2/2003 2 3 Y
ghg2 1/2/2003 3 1 N
afd1 1/2/2003 3 2 N
"),header=TRUE)
cbind(DF, flag = ave(DF$Price, DF$Hour, FUN=function(x) ifelse(x==max(x),
1, 0)))
Unit Day Hour Price Flag flag
1 afd1 1/2/2003 1 1 N 0
2 afd1 1/2/2003 1 2 N 0
3 afd1 1/2/2003 1 3 N 0
4 afd1 1/2/2003 1 4 Y 1
5 dcf1 1/2/2003 2 2 N 0
6 dcf1 1/2/2003 2 3 Y 1
7 dcf1 1/2/2003 2 1 N 0
8 dcf1 1/2/2003 2 2 N 0
9 dcf1 1/2/2003 2 3 Y 1
10 ghg2 1/2/2003 3 1 N 0
11 afd1 1/2/2003 3 2 N 1
On Thu, Jun 7, 2012 at 4:17 PM, jcrosbie <ja...@crosb.ie> wrote:
> For a given hour I want to be able to add a new column called flag. The
> flag column will flag the highest price in a given hour. Is there a way to
> do this without a loop?
>
> matrix:
> Unit, Day, Hour, Price, Flag
> afd1 1/2/2003 1 1 N
> afd1 1/2/2003 1 2 N
> afd1 1/2/2003 1 3 N
> afd1 1/2/2003 1 4 Y
> dcf1 1/2/2003 2 2 N
> dcf1 1/2/2003 2 3 Y
> dcf1 1/2/2003 2 1 N
> dcf1 1/2/2003 2 2 N
> dcf1 1/2/2003 2 3 Y
> ghg2 1/2/2003 3 1 N
> afd1 1/2/2003 3 2 N
> .....
>
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/flagging-values-without-a-loop-tp4632689.html
> Sent from the R help mailing list archive at Nabble.com.
>
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