I have two variables, key and value, and I want to add them as a key/value pair to a list:
key = "width"
value = 32
mylist = list()
mylist$key = value
The result is this:
mylist
# $key
# [1] 32
But I would like this instead:
mylist
# $width
# [1] 32
How can I do this?
R lists can be thought of as hashes- vectors of objects that can be accessed by name. Using this approach you can add a new entry to the list like so:
key <- "width"
value <- 32
mylist <- list()
mylist[[ key ]] <- value
Here we use the string stored in the variable key to access a position in the list much like using the value stored in a loop variable i to access a vector through:
vector[ i ]
The result is:
myList
$width
[1] 32
The setNames() built-in function makes it easy to create a hash from given key and value lists. (Thanks to Nick K for the better suggestion.)
Usage: hh <- setNames(as.list(values), keys)
Example:
players <- c("bob", "tom", "tim", "tony", "tiny", "hubert", "herbert")
rankings <- c(0.2027, 0.2187, 0.0378, 0.3334, 0.0161, 0.0555, 0.1357)
league <- setNames(as.list(rankings), players)
Then accessing the values through the keys is easy:
league$bob [1] 0.2027 league$hubert [1] 0.0555
List elements in R can be named. So in your case just do
> mylist = list()
> mylist$width = value
When R encounters this code
> l$somename=something
where l is a list. It appends to a list an element something, and names it with name somename. It is then can be accessed by using
> l[["somename"]]
or
> l$somename
The name can be changed with command names:
> names(l)[names(l)=="somename"] <- "othername"
Or if you now the position of the element in the list by:
> names(l)[1] <- "someothername"
We can use R's list data structure to store data in the form of key-value pair.
Syntax:
ObjectName<-list("key"= value)
Example:
mylist<-list("width"=32)
also, refer example: "https://github.com/WinVector/zmPDSwR/blob/master/Statlog/GCDSteps.R"
