在函數內如何正確地將參數作為R中的數據屬性傳遞？

Question

我想編寫一個返回數據主體特定屬性的函數，如下所示

dem <- function(sale, attToCall = "year" ){
return(sale$attToCall)
}

aa <- data.frame("month" = sample(1:12, 10),"year" = sample(1990:2016, 10))

dem(aa, attToCall = "year") 

不起作用，有人可以解決嗎？

Answer 1

dem <- function(sale, attToCall = "year" ){
  return(sale[,attToCall])
}

aa <- data.frame("month" = sample(1:12, 10),"year" = sample(1990:2016, 10))

dem(aa, attToCall = "year") 

[1] 2012 2004 2010 2001 1995 1995 2015 2015 2009 1997