Dear all, I would like to ask one question related to statistics, for specifically on defining dummy variables. As of now, I have come across 3 different kind of dummy variables (assuming I am working with Seasonal dummy, and number of season is 4):
> dummy1 <- diag(4) > for(i in 1:3) dummy1 <- rbind(dummy1, diag(4)) > dummy1 <- dummy1[,-4] > > dummy2 <- dummy1 > dummy2[dummy2 == 0] = -1/(4-1) > > dummy3 <- dummy1 - 1/4 > > head(dummy1) [,1] [,2] [,3] [1,] 1 0 0 [2,] 0 1 0 [3,] 0 0 1 [4,] 0 0 0 [5,] 1 0 0 [6,] 0 1 0 > head(dummy2) [,1] [,2] [,3] [1,] 1.0000000 -0.3333333 -0.3333333 [2,] -0.3333333 1.0000000 -0.3333333 [3,] -0.3333333 -0.3333333 1.0000000 [4,] -0.3333333 -0.3333333 -0.3333333 [5,] 1.0000000 -0.3333333 -0.3333333 [6,] -0.3333333 1.0000000 -0.3333333 > head(dummy3) [,1] [,2] [,3] [1,] 0.75 -0.25 -0.25 [2,] -0.25 0.75 -0.25 [3,] -0.25 -0.25 0.75 [4,] -0.25 -0.25 -0.25 [5,] 0.75 -0.25 -0.25 [6,] -0.25 0.75 -0.25 Now I want to know which type of dummy definition is called Centered dummy and why it is called so? Is it equivalent to use any of the above definitions (atleast 2nd and 3rd?) It would really be very helpful if somebody point any suggestion and clarification. Thanks and regards, [[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.