[R ] = 과 <- 의 차이

난 R의 =과 <- 이 동일한 줄 알았는데.. =에서는 최상위 레벨에서만 사용가능하다!!

http://stat.ethz.ch/R-manual/R-patched/library/base/html/assignOps.html

The operators <- and = assign into the environment in which they are evaluated. The operator <- can be used anywhere, whereas the operator = is only allowed at the top level (e.g., in the complete expression typed at the command prompt) or as one of the subexpressions in a braced list of expressions.