R在cthon中有像'python'或'map'那样的'dict'吗？

Question

I am new to R programming. After checking some tutorial I picked up most things I needed, but one thing is still missing: the data structure map.

Does everybody know if R has dict? In which I can store (key, value) pairs?

Thanks!!

Answer 1

Yes it does and it is called list .

> x <- list(a=1, b="foo", c=c(1,1,2,3,5))
> x
$a
[1] 1

$b
[1] "foo"

$c
[1] 1 1 2 3 5

In Python it is called dict , for what it's worth.

Answer 2

Environments are also a candidate, and in many cases the best option.

e<-new.env(hash=T)
e$a<-1
e$b<-2

R> e$a
[1] 1

The disadvantage of a list is that it is a linear search.

Answer 3

有哈希包..

Answer 4

Since array/vector elements can be named, you get some of the properties of a map/dictionary builtin.

x <- c(apple = 1, banana = 99, "oranges and lemons" = 33)
x["apple"]
x[c("bananas", "oranges and lemons")]
x[x == 99]

(If your values are of different types, then you need to use a list instead of a vector.)

Answer 5

The hash package as aforementioned does add a little overhead but does provide a flexible, intuitive methods for accessing the map/hash/dictionary. It should be very easy for users from another language to grok it.

A list is the best solution if the list has a small number of elements. (<200 or so).

An environment is best to use if you absolutely cannot tolerate a little overhead AND you do not want the flexible, intuitive methods.

The hash package is the best in most situations.

C-