[R] Use a text variable's value to specify another varaible?

[Marc Schwartz]

On Fri, 2007-01-26 at 09:48 -0600, Ben Fairbank wrote:
> Greetings guRus --

> If a variable, e.g., 'varname', is a character string, e.g. varname <-
> "datavector", and I want to apply a function, such as table(), to
> datavector, what syntax or method will do so using only the variable
> varname?  This seems similar to indirect addressing, but I have not seen
> a method for it in the R manuals.  Is there a general name for such
> indirect reference that one might search for?

> (This came up while writing a function that takes the value of 'varname'
> from the keyboard and then applies functions to it.)

> With thanks for any solution,

> Ben Fairbank


See ?get and ?assign


datavector <- 1:10
varname <- "datavector"

> get(varname)
 [1]  1  2  3  4  5  6  7  8  9 10

> log10(get(varname))
 [1] 0.0000000 0.3010300 0.4771213 0.6020600 0.6989700 0.7781513
 [7] 0.8450980 0.9030900 0.9542425 1.0000000


and/or

assign(varname, letters)

> datavector
 [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q"
[18] "r" "s" "t" "u" "v" "w" "x" "y" "z"

> get(varname)
 [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q"
[18] "r" "s" "t" "u" "v" "w" "x" "y" "z"


HTH,

Marc Schwartz