attach() inside function

Question

I'd like to give a params argument to a function and then attach it so that I can use a instead of params$a everytime I refer to the list element a.

run.simulation<-function(model,params){ attach(params) # # Use elements of params as parameters in a simulation detach(params) } 

Is there a problem with this? If I have defined a global variable named c and have also defined an element named c of the list "params" , whose value would be used after the attach command?

Answer 1

Noah has already pointed out that using attach is a bad idea, even though you see it in some examples and books. There is a way around. You can use "local attach" that's called with. In Noah's dummy example, this would look like

with(params, print(a)) 

which will yield identical result, but is tidier.

Answer 2

Another possibility is:

run.simulation <- function(model, params){     # Assume params is a list of parameters from      # "params <- list(name1=value1, name2=value2, etc.)"     for (v in 1:length(params)) assign(names(params)[v], params[[v]])     # Use elements of params as parameters in a simulation }