List updating

List updating is useful when we need to modify the original list but do not want to repeat the data.

devs <- 
  list(
    p1=list(name="Ken",age=24,
      interest=c("reading","music","movies"),
      lang=list(r=2,csharp=4,python=3)),
    p2=list(name="James",age=25,
      interest=c("sports","music"),
      lang=list(r=3,java=2,cpp=5)),
    p3=list(name="Penny",age=24,
      interest=c("movies","reading"),
      lang=list(r=1,cpp=4,python=2)))

list.update

list.update partially modifies the given list by a number of lists resulted from expressions.

str(list.update(devs,age=age+1))

# List of 3
#  $ p1:List of 4
#   ..$ name    : chr "Ken"
#   ..$ age     : num 25
#   ..$ interest: chr [1:3] "reading" "music" "movies"
#   ..$ lang    :List of 3
#   .. ..$ r     : num 2
#   .. ..$ csharp: num 4
#   .. ..$ python: num 3
#  $ p2:List of 4
#   ..$ name    : chr "James"
#   ..$ age     : num 26
#   ..$ interest: chr [1:2] "sports" "music"
#   ..$ lang    :List of 3
#   .. ..$ r   : num 3
#   .. ..$ java: num 2
#   .. ..$ cpp : num 5
#  $ p3:List of 4
#   ..$ name    : chr "Penny"
#   ..$ age     : num 25
#   ..$ interest: chr [1:2] "movies" "reading"
#   ..$ lang    :List of 3
#   .. ..$ r     : num 1
#   .. ..$ cpp   : num 4
#   .. ..$ python: num 2

str(list.update(devs,interest=NULL,lang=NULL,nlang=length(lang)))

# List of 3
#  $ p1:List of 3
#   ..$ name : chr "Ken"
#   ..$ age  : num 24
#   ..$ nlang: int 3
#  $ p2:List of 3
#   ..$ name : chr "James"
#   ..$ age  : num 25
#   ..$ nlang: int 3
#  $ p3:List of 3
#   ..$ name : chr "Penny"
#   ..$ age  : num 24
#   ..$ nlang: int 3