<我的代码>中的错误:"closure"类型的对象不可子集化 [英] Error in <my code> : object of type 'closure' is not subsettable
问题描述
我终于能够为我的抓取编写代码.它似乎运行良好，然后突然再次运行时，出现以下错误消息:
Error in url[i] = paste("http://en.wikipedia.org/wiki/", gsub(" ", "_", :
object of type 'closure' is not subsettable
我不确定为什么在代码中什么都没改变.
请告知.
library(XML)
library(plyr)
names <- c("George Clooney", "Kevin Costner", "George Bush", "Amar Shanghavi")
for(i in 1:length(names)) {
url[i] = paste('http://en.wikipedia.org/wiki/', gsub(" ","_", names[i]) , sep="")
# some parsing code
}
通常，此错误消息表示您已尝试在函数上使用索引.您可以使用例如
来重现此错误消息.mean[1]
## Error in mean[1] : object of type 'closure' is not subsettable
mean[[1]]
## Error in mean[[1]] : object of type 'closure' is not subsettable
mean$a
## Error in mean$a : object of type 'closure' is not subsettable
错误消息中提到的闭包是(松散地)函数和调用函数时存储变量的环境.
在这种特定情况下，如Joshua所述，您正在尝试访问 url 用作变量.如果定义一个名为url的变量，则错误消失了.
作为一个很好的实践，您通常应该避免在base-R函数之后命名变量. (调用变量 data 是此错误的常见来源.)
尝试对运算符或关键字进行子集化时，存在一些相关的错误.
`+`[1]
## Error in `+`[1] : object of type 'builtin' is not subsettable
`if`[1]
## Error in `if`[1] : object of type 'special' is not subsettable
如果您在shiny中遇到此问题，则最可能的原因是您尝试使用reactive表达式，而没有使用括号将该函数作为函数调用.
library(shiny)
reactive_df <- reactive({
data.frame(col1 = c(1,2,3),
col2 = c(4,5,6))
})
虽然我们经常像使用数据框一样使用闪亮的反应式表达式，但实际上它们是返回数据框(或其他对象)的函数.
isolate({
print(reactive_df())
print(reactive_df()$col1)
})
col1 col2
1 1 4
2 2 5
3 3 6
[1] 1 2 3
但是，如果我们尝试在不带括号的情况下对其进行子集化，那么实际上是在尝试对函数进行索引，并且会出现错误:
isolate(
reactive_df$col1
)
Error in reactive_df$col1 : object of type 'closure' is not subsettable
I was finally able to work out the code for my scraping. It seemed to be working fine and then all of a sudden when I ran it again, I got the following error message:
Error in url[i] = paste("http://en.wikipedia.org/wiki/", gsub(" ", "_", :
object of type 'closure' is not subsettable
I am not sure why as I changed nothing in my code.
Please advise.
library(XML)
library(plyr)
names <- c("George Clooney", "Kevin Costner", "George Bush", "Amar Shanghavi")
for(i in 1:length(names)) {
url[i] = paste('http://en.wikipedia.org/wiki/', gsub(" ","_", names[i]) , sep="")
# some parsing code
}
In general this error message means that you have tried to use indexing on a function. You can reproduce this error message with, for example
mean[1]
## Error in mean[1] : object of type 'closure' is not subsettable
mean[[1]]
## Error in mean[[1]] : object of type 'closure' is not subsettable
mean$a
## Error in mean$a : object of type 'closure' is not subsettable
The closure mentioned in the error message is (loosely) the function and the environment that stores the variables when the function is called.
In this specific case, as Joshua mentioned, you are trying to access the url function as a variable. If you define a variable named url, then the error goes away.
As a matter of good practise, you should usually avoid naming variables after base-R functions. (Calling variables data is a common source of this error.)
There are several related errors for trying to subset operators or keywords.
`+`[1]
## Error in `+`[1] : object of type 'builtin' is not subsettable
`if`[1]
## Error in `if`[1] : object of type 'special' is not subsettable
If you're running into this problem in shiny, the most likely cause is that you're trying to work with a reactive expression without calling it as a function using parentheses.
library(shiny)
reactive_df <- reactive({
data.frame(col1 = c(1,2,3),
col2 = c(4,5,6))
})
While we often work with reactive expressions in shiny as if they were data frames, they are actually functions that return data frames (or other objects).
isolate({
print(reactive_df())
print(reactive_df()$col1)
})
col1 col2
1 1 4
2 2 5
3 3 6
[1] 1 2 3
But if we try to subset it without parentheses, then we're actually trying to index a function, and we get an error:
isolate(
reactive_df$col1
)
Error in reactive_df$col1 : object of type 'closure' is not subsettable
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