I have encountered the following problem: I need to extract from a list of lists equally named compenents who happen to be 'one row' data frames. a trivial example would be:
a <- list(list( df = data.frame(A = 1, B = 2, C = 3)), list(df = data.frame(A = 4,B = 5,C = 6))) I want the extracted compenents to fill up a matrix or data frame row by row. the obvious thing to do seems: b <- sapply(a, "[[", "df") b <- t(b) now `b' looks all right: b class(b) but it turns out that all elements in this matrix are one element lists: class(b[1,1]) which prevents any further standard processing of `b' (like `colMeans', e.g.) question 1: is their a straightforward way to enforce that `b' contains simple numbers as elements right from the start (instead of something like apply(b, 1:2, "class<-", "numeric") afterwards)? question 2: should not sapply do this further 'simplification' anyway in a situation like this (matrix elements turn out to be one-element lists)? regards joerg ______________________________________________ R-help@stat.math.ethz.ch 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.