[R] Multiple line commands in R scripting

[David Winsemius]

On Oct 25, 2009, at 8:53 AM, Neil Stewart wrote:

> I'm wondering whether there is a character to let R know to expect  
> more
> input for a command on subsequent lines. Here is an example:
>
> test_1.R:
> x <- c(1,2,3,4)
>    / c(1,2,3,4)
> x
>
> R CMD BATCh test_1.R produces test_1.Rout:
>> x <- c(1,2,3,4)
>>  / c(1,2,3,4)
> Error: unexpected '/' in "  /"
> Execution halted
>
>
> test_2.R:
> x <- c(1,2,3,4) /
>    c(1,2,3,4)
> x
>
> R CMD BATCh test_1.R produces test_2.Rout:
>> x <- c(1,2,3,4) /
> +   c(1,2,3,4)
>> x
> [1] 1 1 1 1
>
> test_2.R works as expected but test_1.R fails because the "/"  
> operator is at
> the start of line 2 not the end of line 1.
>
> Is the some kind of continuation charater one can include in a  
> script so R
> is expecting input on the next line? For example, in other  
> languages, "\"
> works. Without this, one is forced to break lines carefully in the  
> middle of
> a function, for example, to ensure R is expecting more. Any comments  
> very
> welcome.

R waits for a complete command. Leave the "/" at the end of the first  
line and it will then  be incomplete. It is also common to see ","'s  
(commas) at the end of lines in scripts.

test_1.R:
x <- c(1,2,3,4)/
    c(1,2,3,4)
x
# Should "work"

> Thank you,
> Neil.
>
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> and provide commented, minimal, self-contained, reproducible code.

David Winsemius, MD
Heritage Laboratories
West Hartford, CT