So, what's the easiest way to add a column to a dataframe? Just do it. Here is a really simple example to illustrate:
> foo <- data.frame(x=1:4,y=2:5) > foo x y 1 1 2 2 2 3 3 3 4 4 4 5 > foo$z <- c(NA,diff(foo$x)) > foo x y z 1 1 2 NA 2 2 3 1 3 3 4 1 4 4 5 1 Solutions using apply and sapply are overly complicated for what you requested. If you had to do this for many, many columns a looping solution would be worth it, but for just two columns, it's not. -Don At 12:46 PM +0530 1/10/08, Vishal Belsare wrote: >I have a dataframe say: > >date price_g price_s > 0.34 0.56 > 0.36 0.76 > . . > . . > . . > >and so on. say, 1000 rows. > >Is it possible to add two columns to this dataframe, by computing say >diff(log(price_g) and diff(log(price_s)) ? > >The elements in the first row of these columns cannot be computed, but >can I coerce this to happen and assign a missing value there? It would >be really great if I could do that, because in this case I don't have >to re-index my transformed series to the dates again in a new >dataframe. > >Thanks in anticipation. > > >Vishal Belsare > >______________________________________________ >R-help@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. -- -------------------------------------- Don MacQueen Environmental Protection Department Lawrence Livermore National Laboratory Livermore, CA, USA 925-423-1062 ______________________________________________ R-help@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.
