Converting a text to command

Question

I would like to know if there’s a way to convert a text to a command and execute it. Here’s the concerned part of the script I’m working on:

Var_name<- as.character(data_list[1,1])

U4005 

(data_list contains just names of vectors in a bigger dataframe called vectors)

Comm<-paste(Var_name,”<-“,”vectors$”,Var_name)

Comm

“U4005<-vectors$U4005”

Answer 1

This seems a strange thing to do, but I think you are better off using assign rather than creating "interactive" commands to parse.

assign(Var_name,vectors[[Var_name]])

This way you can loop over your names to pull things out quite easily. You just need to specify that it is the global environment to assign to.

x <- data.frame(a=1:3,b=letters[1:3])
ls()
[1] "x"
invisible(sapply(names(x),function(y) assign(y,x[[y]],.GlobalEnv)))
ls()
[1] "a" "b" "x"
a
[1] 1 2 3
b
[1] a b c
Levels: a b c

Answer 2

The following code should work:

e <- "a <- 1"
eval(parse(text = e))
a
# [1] 1

Does it help?