list.update() partially modifies the given list by a number of lists resulted from expressions.
First, we load the data without any modification.
library(rlist) library(pipeR) people <- list.load("http://renkun.me/rlist-tutorial/data/sample.json") people %>>% list.select(Name, Age) %>>% list.stack
# Name Age # 1 Ken 24 # 2 James 25 # 3 Penny 24
list.stack() converts a list to a data frame with equivalent structure. We will introduce this function later.
Suppose we find that the age of each people is mistakenly recorded, say, 1 year less than their actual ages, respectively, we need to update the original data by refresh the age of each element.
people %>>% list.update(Age = Age + 1) %>>% list.select(Name, Age) %>>% list.stack
# Name Age # 1 Ken 25 # 2 James 26 # 3 Penny 25
list.update() can also be used to exclude certain fields of the elements. Once we update the fields we want to exclude to
NULL, those fields are removed.
people %>>% list.update(Interests = NULL, Expertise = NULL, N = length(Expertise)) %>>% list.stack
# Name Age N # 1 Ken 24 3 # 2 James 25 3 # 3 Penny 24 3