Hi: Here's a ddply solution to your problem (package plyr):
library(plyr) # within group function to apply; assumes that 'none' is first obs in group # x will be the Count variable in the call... subt2 <- function(x) x - x[1] head(df) rep Count stain 1 1 1522.0 none 2 1 147.0 syto 3 1 544.8 sytolec 4 1 2432.6 sytolec 5 1 234.6 sytolec 6 2 5699.8 none ddply(df, .(rep), transform, calib = subt2(Count)) rep Count stain calib 1 1 1522.0 none 0.0 2 1 147.0 syto -1375.0 3 1 544.8 sytolec -977.2 4 1 2432.6 sytolec 910.6 5 1 234.6 sytolec -1287.4 6 2 5699.8 none 0.0 7 2 265.6 syto -5434.2 8 2 329.6 sytolec -5370.2 9 2 383.0 sytolec -5316.8 10 2 968.8 sytolec -4731.0 11 3 2466.8 none 0.0 12 3 1303.0 syto -1163.8 13 3 1290.6 sytolec -1176.2 14 3 110.2 sytolec -2356.6 15 3 15086.8 sytolec 12620.0 HTH, Dennis On Fri, Mar 12, 2010 at 2:27 PM, Sam Albers <tonightstheni...@gmail.com>wrote: > Hello all, > > I have not been able to find an answer to this problem. I feel like it > might > be so simple though that it might not get a response. > > Suppose I have a dataframe like the one I have copied below (minus the > 'calib' column). I wish to create a column like calib where I am > subtracting > the 'Count' when 'stain' is 'none' from all other 'Count' data for every > value of 'rep'. This is sort of analogous to putting a $ in front of the > number that identifies a cell in a spreadsheet environment. Specifically I > need some like this: > > mydataframe$calib <- Count - (Count when stain = none for each value rep) > > Any thoughts on how I might accomplish this? > > Thanks in advance. > > Sam > > Note: I've already calculated the calib column in gnumeric for clarity. > > rep Count stain calib > 1 1522 none 0 > 1 147 syto -1375 > 1 544.8 sytolec -977.2 > 1 2432.6 sytolec 910.6 > 1 234.6 sytolec -1287.4 > 2 5699.8 none 0 > 2 265.6 syto -5434.2 > 2 329.6 sytolec -5370.2 > 2 383 sytolec -5316.8 > 2 968.8 sytolec -4731 > 3 2466.8 none 0 > 3 1303 syto -1163.8 > 3 1290.6 sytolec -1176.2 > 3 110.2 sytolec -2356.6 > 3 15086.8 sytolec 12620 > > -- > ***************************************************** > Sam Albers > Geography Program > University of Northern British Columbia > 3333 University Way > Prince George, British Columbia > Canada, V2N 4Z9 > phone: 250 960-6777 > ***************************************************** > > [[alternative HTML version deleted]] > > ______________________________________________ > 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. > [[alternative HTML version deleted]] ______________________________________________ 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.
