Hi, what is the proper of of "passing a missing value" so I can extract the entire i-th row of a matrix (in a list of lists) without pre-computing the number of cols?
For example, if I know that the matrices have 2 columns, I can do the following: set.seed(1) x0 <- lapply(1:10, function(i) replicate(4, list(matrix(rnorm(10), nc=2)))) lapply(lapply(x0, '[[', 3), '[', i=2, j=1:2) (given that if I don't specify j, I only get the first element) but if the number of columns are variable: x1 <- lapply(1:10, function(i) replicate(4, list(matrix(rnorm(100), nc=sample(c(2, 4, 5, 10), 1))))) what would be the value of J below? lapply(lapply(x1, '[[', 3), '[', i=2, j=J) or should I really stick with: lapply(lapply(x1, '[[', 3), function(x) x[2,]) ? Thank you very much, benilton ______________________________________________ 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.
