On Mon, 2015-11-16 at 20:11 -0500, Paul Grosu wrote: > Hi Everyone, > > Sorry to bother the list with this small request, but I've run into this > issue and was wondering if it could be fixed in the next version of R. > Sorry if it was raised in a previous thread: > > So when I try the following I get an error: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > Error in m[["A3V6HVSALQ835D"]][["stars"]] <- c(1, 23) : > more elements supplied than there are to replace > > As does the following: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- c() > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > Error in m[["A3V6HVSALQ835D"]][["stars"]] <- c(1, 23) : > more elements supplied than there are to replace > > But when I reverse the order, I don't: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > As doesn't the following, with the order reversed for the assignment: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > And when I instantiate it in this way, it does not with the original order: > > > m <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- c() > > m[["A3V6HVSALQ835D"]][['stars']] <- list() > > m[["A3V6HVSALQ835D"]][['profiles']] <- 3 > > m[["A3V6HVSALQ835D"]][['stars']] <- c(1, 23) > > The request is so that order-specific assignments would not throw an error, > and I am using version 3.2.2 of R.
Your example combines two nested calls to the replacement function "[[<-". It is a lot easier to understand what is going wrong if you break this down into two separate function calls. First, the element of m that you want to modify is NULL: > m <- list() > m[["A3V"]] NULL So the expression > m[["A3V"]][['profile']] <- 3 is equivalent to: > tmp <- NULL > tmp[['profile']] <- 3 > m[["A3V"]] <- tmp Inspecting the result: > m $A3V profile 3 > class(m$A3V) [1] "numeric" So m$A3V is a numeric vector and not, as you expected, a list. This behaviour of "[[<-" when applied to NULL objects is documented on the help page: See help("[[<-") The solution is to create m[["A3V"]] as a list before modifying its elements: > m <- list() > m[["A3V"]] <- list() ... Martyn > Thank you, > Paul > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel ----------------------------------------------------------------------- This message and its attachments are strictly confidenti...{{dropped:8}} ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel