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Learning a new language usually starts with outputting a "Hello, World!" program. The R language "Hello, World!" program code is as follows: ## Example (helloworld.R) myString **Note:** R language assignment uses the left arrow > > **Note:** The most common script file extension for R is .R. > > > For example: > > hello.R data_analysis.R stock.R > Although .r can also be used, the community mainstream almost exclusively uses .R. ### Variables Valid variable names in R language consist of letters, numbers, and dots . or underscores _. Variable names start with a letter or a dot. | Variable Name | Valid | Reason | | --- | --- | --- | | var_name2. | Valid | Starts with a character, composed of letters, numbers, underscores, and dots | | var_name% | Invalid | % is an illegal character | | 2var_name | Invalid | Cannot start with a number | | .var_name, var.name | Valid | Can start with a dot, but be careful not to follow the dot with a number | | .2var_name | Invalid | Cannot have a number after the dot | | _var_name | Invalid | Cannot start with an underscore | ### Variable Assignment The latest versions of R language assignment can use left arrow : ## Example # Use equal sign = for assignment > var.1 =c(0,1,2,3) >print(var.1) 0 1 2 3 # Use left arrow var.2 print(var.2) "learn""R" # Use right arrow -> for assignment >c(TRUE,1)-> var.3 >print(var.3) 1 1 To view defined variables, you can use the **ls()** function: ## Example >print(ls()) "var.1""var.2""var.3" To delete variables, you can use the **rm()** function: ## Example >rm(var.3) >print(ls()) "var.1""var.2" > In the previous chapter, we learned how to install the R programming environment. Next, we will introduce R language interactive programming and file script programming. ### Interactive Programming We only need to execute the R command in the command line to enter the interactive programming window: R After executing this command, the R language interpreter will be invoked. We can enter code after the > symbol. !(https