Error in cool_function[1] : object of type 'closure' is not subsettable

问题：

#函数怎么能被索引那，函数计算返回的结果有可能是可以索引的。

#define function
cool_function <- function(x) {
  x <- x*5
  return(x)
}


#define data
data <- c(2, 3, 3, 4, 5, 5, 6, 9)

#apply function to data
cool_function(data)

#attempt to get first element of function
cool_function[1]

#其他类似错误

#attempt to subset mean function
mean[1]

Error in mean[1] : object of type 'closure' is not subsettable

#attempt to subset standard deviation function
sd[1]

Error in sd[1] : object of type 'closure' is not subsettable

#attempt to subset table function
tabld[1]

Error in table[1] : object of type 'closure' is not subsettable

解决：

#typeof获取数据类型

#print object type of function
typeof(cool_function)

[1] "closure"

#正确的操作

#apply function to just first element in vector
cool_function(data[1])


#apply function to every element in vector
cool_function(data)

完整错误：

> #define function
> cool_function <- function(x) {
+ x <- x*5
+ return(x)
+ }
>
>
> #define data
> data <- c(2, 3, 3, 4, 5, 5, 6, 9)
>
> #apply function to data
> cool_function(data)
[1] 10 15 15 20 25 25 30 45
>
> #attempt to get first element of function
> cool_function[1]
Error in cool_function[1] : object of type 'closure' is not subsettable
>