请问：typeof()、mode()、class()的区别？

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关键词：mode type Mod ODE

R的这个类型确实有些不好理解。
我的粗略的理解：
mode是R存诸对象的类型， class 的概念是沿袭面向对象编程的概念而来，是一个更抽象的概念。typeof 和mode 相似，但是好像比mode分得更精细。

从精细度上说，typeof>mode>class.

对R了解不多，不一定对。

还是感谢版主大人了！

mode()：模式，常见的有"logical", "integer", "double", "complex", "raw", "character", "list", "expression", "name", "symbol" and "function".
class():类，In R every 'object' has a mode and a class.

Modes have the same set of names as types (see typeof) except that

• types "integer" and "double" are returned as "numeric".
  
• types "special" and "builtin" are returned as "function".
  
• type "symbol" is called mode "name".
  
• type "language" is returned as "("  or  "call".
  from:?mode()
  也可以参考：http://stackoverflow.com/questio ... -and-class-and-type
  
  

  我这里用个因子例子来说明，希望能讲清楚 > gl(2,5)            #新建一个因子 [1] 1 1 1 1 1 2 2 2 2 2 Levels: 1 2 > class(gl(2,5))   #查看变量的类，显示为因子； [1] "factor" > mode(gl(2,5))     #查看数据大类，显示为数值型； [1] "numeric" > typeof(gl(2,5))    #查看数据细类，显示为整数型； [1] "integer" 来自：http://f.dataguru.cn/thread-99785-1-1.html

  
  
  

我这里用个因子例子来说明，希望能讲清楚
> gl(2,5)            #新建一个因子
[1] 1 1 1 1 1 2 2 2 2 2
Levels: 1 2
> class(gl(2,5))   #查看变量的类，显示为因子；
[1] "factor"
> mode(gl(2,5))     #查看数据大类，显示为数值型；
[1] "numeric"
> typeof(gl(2,5))    #查看数据细类，显示为整数型；
[1] "integer"
来自：http://f.dataguru.cn/thread-99785-1-1.html

zhengbo8 发表于 2013-8-19 18:47
还是感谢版主大人了！

都开始折腾R了。

[img][/img]

看以下输出结果：

> df=data.frame(c1=letters[1:3], c2=1:3, c3=c(1,-1,3.0), stringsAsFactors=F)
> sapply(df, mode)
         c1          c2          c3
"character"   "numeric"   "numeric"
> sapply(df, class)
         c1          c2          c3
"character"   "integer"   "numeric"
> sapply(df, typeof)
         c1          c2          c3
"character"   "integer"    "double"

可以发现，在展现数据的细节上，mode<class<typeof。

'mode' is a mutually exclusive classification of objects according to their basic structure. The 'atomic' modes are numeric, complex, character and logical. Recursive objects have modes such as 'list' or 'function' or a few others. An object has one and only one mode.

'class' is a property assigned to an object that determines how generic functions operate with it. It is not a mutually exclusive classification. If an object has no specific class assigned to it, such as a simple numeric vector, it's class is usually the same as its mode, by convention.

Changing the mode of an object is often called 'coercion'. The mode of an object can change without necessarily changing the class. e.g.

这个答案参见下面这个网页的第2个回答 我觉得说得比较好https://stackoverflow.com/questions/35445112/what-is-the-difference-between-mode-and-class-in-r