Re: [R] flagging values without a loop

Hi. Yes it is possible. Here is one approach: DF <- read.table(textConnection(" Unit DayHour Price Flag afd11/2/20031 1 N afd11/2/20031 2 N afd11/2/20031 3 N afd11/2/20031 4 Y dcf11/2/2003

Re: [R] flagging values without a loop

In two steps, you could use ave() to split by hour and find the maximum of price and then use an ifelse clause on the resulting vector to see when that actually equals the given price and assign "Y"/"N" appropriately, I'll leave the implementation as an exercise to the reader :-) Best, Michael O

[R] flagging values without a loop

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 afd11/2/20031 1 N afd11/2/20031 2