r - Why cv.tree() can't find this object when called from inside a function? -

i seem have namespace or scope issue when calling cv.tree() inside function:

library(tree) library(islr) carseats$high = ifelse(sales <= 8, "no", "yes")  mytreecv = function(formula, mydata) {   set.seed(2)   tree.carseats = tree(formula, mydata)   cv.carseats = cv.tree(tree.carseats, fun=prune.misclass) } 

when run mytreecv() error:

> mytreecv(high ~ . - sales, carseats) error in is.data.frame(data) (from #5) : object 'mydata' not found 

the cv.tree() call model.frame(object) fails. same function code works when call each line r prompt.

not sure why happens can fixed creating tree argument model = t. using example above:

mytreecv = function(formula, mydata) {   set.seed(2)   tree.carseats = tree(formula, mydata, model = t)   cv.carseats = cv.tree(tree.carseats, fun=prune.misclass) } 

answer found here: http://florence.acadiau.ca/collab/hugh_public/index.php?title=r:putting_cv.tree_inside_a_function&redirect=no