how to get value when a variable name is passed as a string

Question

i write this code in R

paste(\"a\",\"b\",\"c\") 

which returns the value \"abc\"

Variable abc has a value

Answer 1

paste("a","b","c") gives "a b c" not "abc"

Anyway, I think you are looking for get():

> abc <- 5
> get("abc")
[1] 5

Answer 2

Here is an example to demonstrate eval() and get(eval())

a <- 1
b <- 2

var_list <- c('a','b')

for(var in var_list)
{
  print(paste(eval(var),' : ', get(eval(var))))
}

This gives:

[1] "a  :  1"
[1] "b  :  2"

Answer 3

This is certainly one of the most-asked questions about the R language, along with its evil twin brother "How do I turn x='myfunc' into an executable function?" In summary, get, parse, eval , expression are all good things to learn about. The most useful (IMHO) and least-well-known is do.call , which takes care of a lot of the string-to-object conversion work for you.

Answer 4

An addition to Sacha's answer. If you want to assign a value to an object "abc" using paste():

assign(paste("a", "b", "c", sep = ""), 5)