On 12/11/2008 7:59 AM, David Croll wrote:
Hello dear R people!
Several times it occurred to me that a function that uses a variable name as a
parameter would be helpful, but I did not find out how to write such a
function. I have experience in several programming language, but I did not come
across a helpful trick...
What I want to have is...
a <- 12 # starting value
add <- function(variable,increment) {
variable <- variable + increment
}
# by typing a and 25 for example, you specify that 25 will be added to the
variable a...
add(a,25)
# the new a equals 12 + 25 = 37
Thanks for all the help – I'll try to give my advice when I get across a
problem I can solve!
That's not a good idea: it looks as though you're trying to fake "call
by reference" in a call by value language. R is flexible enough to do
it (use substitute() to change the arg into a string, get() to get the
old value, assign() to put it back), but the behaviour will be really
weird, and you'll probably run into problems later. R is not C.
Duncan Murdoch
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