Hi Michael, Your answer was very interesting, thank you! However, I tried it and the result was:
> df <- read.table(file="df.txt", head=T, sep="\t") > df i j k 1 1 2 5.2 2 1 3 9.1 3 1 4 8.0 4 1 5 2.3 5 1 6 8.4 6 2 3 6.6 7 2 4 7.4 8 2 5 7.1 9 2 6 5.5 10 3 4 4.1 11 3 5 3.9 12 3 6 9.2 13 4 5 8.5 14 4 6 7.6 15 5 6 9.9 > x <- with(df, matrix(NA, ncol= max(j), nrow=max(i)+1)) > x[with(df, i), with(df, j)] <- with(df, k) > x [,1] [,2] [,3] [,4] [,5] [,6] [1,] NA 8.4 8.4 8.4 8.4 8.4 [2,] NA 5.5 5.5 5.5 5.5 5.5 [3,] NA 9.2 9.2 9.2 9.2 9.2 [4,] NA 7.6 7.6 7.6 7.6 7.6 [5,] NA 9.9 9.9 9.9 9.9 9.9 [6,] NA NA NA NA NA NA It seems that R only reads the values [1,6], [2,6], [3,6], [4,6], and [5,6] and repeats them for every postition of the row... Still trying to find why and how to change it, but if someone finds a solution it will be appreciated -- View this message in context: http://r.789695.n4.nabble.com/built-a-lower-triangular-matrix-from-dataframe-tp4390813p4393528.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.