在R中分配数据帧时使用'='与'<-'运算符的不同行为 [英] Different behavior in using '=' versus '<-' operator while assigning a dataframe in R

问题描述

我想知道为什么在分配dataframe时使用=和<-会有区别.

I would like to know why there is a difference between using = and <- while assigning a dataframe.

情况a:使用=

set.seed(100);a <- data.frame(a1=rnorm(10),a2=sample(c(1,0),10,replace=TRUE))

案例b:使用<-

set.seed(100);b <- data.frame(b1 <- rnorm(10),b2 <- sample(c(1,0),10,replace=TRUE))

为什么有以下区别?为什么第二种方法不保留变量/列名?

Why is there the following difference? Why does not second method retain the variable/column names?

> a
           a1 a2
1 -0.50219235  0
2  0.13153117  0
3 -0.07891709  1
4  0.88678481  1
5  0.11697127  0

>b
  b1....rnorm.5. b2....sample.c.1..0...5..replace...TRUE.
1    -0.50219235                                        0
2     0.13153117                                        0
3    -0.07891709                                        1
4     0.88678481                                        1
5     0.11697127                                        0

推荐答案

在函数内部，'='用作命名或将函数引用到具有特定名称的变量，而<-则是分配函数.当R运行时，它将首先在您的函数参数中解析'<-'函数，然后将在等号或全表达式左侧的东西处命名变量，在这种情况下为"b1 <-rnorm(10) .最后它将解析该功能(在本例中为data.frame).

Within functions '=' is used as naming or referring the function to a variable of a particular name and <- refers to the assignment function. When R runs it will first resolve '<-" functions within your function parameters. It will then name the variable wither the thing to the left of the equal sign or the full expression in this case "b1 <- rnorm(10)". Finally it will resolve the function (in this case data.frame).

您几乎总是想在函数中使用'='.在某些情况下，您可能希望嵌套一个赋值<-"，但这通常会使您的代码难以理解.

You almost always want to use the '=' within a function. There can be cases where you may want to nest an assignment "<-" but normally this will make your code ridiculous to read.

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