Evaluation of an expression as function argument

Sebastien Bihorel wrote:

Dear R-users,

I would like to know if is it possible to set a function argument as 
an evaluated expression. I have tried several syntaxes, including the 
following example, but could not get it anything to run. The plot 
function is used here but I would like to later apply the same 
approach to other functions.

##########################
items <- c(expression(col=2),expression(pch=2))

for (in in seq(2)) {
 plot(1:10, eval(items[i]))
}
##########################

Way 1:

for(i in seq(2))
  do.call("plot", c(list(1:10), as.list(items[i])))


Way 2 is perhaps easier for you:


items <- list(col=2, pch=2)
for (i in seq(2))
  do.call("plot", c(list(1:10), items[i]))


Ways 3...n up to others...


Uwe Ligges

Thanks in advance for your input.

Sebastien