I would like to de-mean the 'vector' column of the following dataframe by factor:
set.seed(5444) vector <- rnorm(1:10) factor <- rep(1:2,5) test.df <- data.frame(factor, vector) which is: factor vector 1 1 -0.4963935 2 2 -2.0768182 3 1 -1.5822224 4 2 0.8025474 5 1 0.3504199 6 2 0.2358464 7 1 -0.3989443 8 2 -0.3692544 9 1 -0.3174586 10 2 1.4305431 Using the by() command, I get: > by(test.df$vector, test.df$factor, function(x) {x - mean(x)}) test.df$factor: 1 [1] -0.007473699 -1.093302612 0.839339673 0.089975488 0.171461151 -------------------------------------------------------------------------------------------------- test.df$factor: 2 [1] -2.0813911 0.7979745 0.2312735 -0.3738272 1.4259702 > My question is: Is there a way to have this output put back to the dataframe? I.e to make by(), or some other command, return me a vector of length 10 whose values x' correspond to x'_1 = x_1 - mean(x | factor1), x'_2 = x_2 - mean(x | factor2),... Thanks in advance for the help, and apologies for the poor notation. Vassilis -- View this message in context: http://r.789695.n4.nabble.com/Can-the-by-function-return-a-single-column-tp3089231p3089231.html Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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.