| 变量名 | 有效性 | 原因 |
| var_name2. | 有效 | 有字母、数字、点和下划线 |
| var_name% | 无效 | 具有字符"%"。只允许使用点 (.) 和下划线。 |
| 2var_name | 无效 | 以数字开头 |
|
.var_name,
var.name
|
有效 | 可以以点(.)开头，但点(.)后面不能跟数字。 |
| .2var_name | 无效 | 起始点后跟一个数字，使其无效。 |
| _var_name | 无效 | 以 _ 开头，这是无效的 |
# Assignment using equal operator. var.1 = c(0,1,2,3) # Assignment using leftward operator. var.2 <-c("learn","R") # Assignment using rightward operator. c(TRUE,1)-> var.3 print(var.1) cat ("var.1 is ", var.1 ,"\n") cat ("var.2 is ", var.2 ,"\n") cat ("var.3 is ", var.3 ,"\n")
[1] 0 1 2 3 var.1 is 0 1 2 3 var.2 is learn R var.3 is 1 1
var_x <-"Hello" cat("The class of var_x is ",class(var_x),"\n") var_x <-34.5 cat(" Now the class of var_x is ",class(var_x),"\n") var_x <-27L cat(" Next the class of var_x becomes ",class(var_x),"\n")
The class of var_x is character Now the class of var_x is numeric Next the class of var_x becomes integer
print(ls())
[1] "my var" "my_new_var" "my_var" "var.1" [5] "var.2" "var.3" "var.name" "var_name2." [9] "var_x" "varname"
# List the variables starting with the pattern "var".
print(ls(pattern = "var"))
[1] "my var" "my_new_var" "my_var" "var.1" [5] "var.2" "var.3" "var.name" "var_name2." [9] "var_x" "varname"
print(ls(all.name = true))
[1] ".cars" ".Random.seed" ".var_name" ".varname" ".varname2" [6] "my var" "my_new_var" "my_var" "var.1" "var.2" [11]"var.3" "var.name" "var_name2." "var_x"
rm(var.3) print(var.3)
[1] "var.3" Error in print(var.3) : object 'var.3' not found
rm(list = ls()) print(ls())
character(0)
