options(width = 120) library('data.tree') library(yaml) osList <- yaml.load_file("users.yaml") osNode <- as.Node(osList) osNode$Do(function(node) node$cumUser <- Cumulate(node,attribute = "users",aggFun = sum)) #birds$species <- function(self) sum(sapply(self$children, function(x) x$species)) print(osNode)