Split code over multiple lines in an R script

Bah, comments are too small. Anyway, @Dirk is very right.

R doesn't need to be told the code starts at the next line. It is smarter than Python ;-) and will just continue to read the next line whenever it considers the statement as "not finished". Actually, in your case it also went to the next line, but R takes the return as a character when it is placed between "".

Mind you, you'll have to make sure your code isn't finished. Compare

a <- 1 + 2
+ 3

with

a <- 1 + 2 +
3

So, when spreading code over multiple lines, you have to make sure that R knows something is coming, either by :

leaving a bracket open, or

ending the line with an operator

When we're talking strings, this still works but you need to be a bit careful. You can open the quotation marks and R will read on until you close it. But every character, including the newline, will be seen as part of the string :

x <- "This is a very
long string over two lines."
x
## [1] "This is a very\nlong string over two lines."
cat(x)
## This is a very
## long string over two lines.

That's the reason why in this case, your code didn't work: a path can't contain a newline character (\n). So that's also why you better use the solution with paste() or paste0() Dirk proposed.

You are not breaking code over multiple lines, but rather a single identifier. There is a difference.

For your issue, try

R> setwd(paste("~/a/very/long/path/here",
               "/and/then/some/more",
               "/and/then/some/more",
               "/and/then/some/more", sep=""))

which also illustrates that it is perfectly fine to break code across multiple lines.

Dirk's method above will absolutely work, but if you're looking for a way to bring in a long string where whitespace/structure is important to preserve (example: a SQL query using RODBC) there is a two step solution.

1) Bring the text string in across multiple lines

long_string <- "this
is 
a 
long
string
with
whitespace"

2) R will introduce a bunch of \n characters. Strip those out with strwrap(), which destroys whitespace, per the documentation:

strwrap(long_string, width=10000, simplify=TRUE)

By telling strwrap to wrap your text to a very, very long row, you get a single character vector with no whitespace/newline characters.

For that particular case there is file.path :

File <- file.path("~", 
  "a", 
  "very", 
  "long",
  "path",
  "here",
  "that",
  "goes",
  "beyond",
  "80",
  "characters",
  "and",
  "then",
  "some",
  "more")
setwd(File)

The glue::glue function can help. You can write a string on multiple lines in a script but remove the line breaks from the string object by ending each line with \\:

glue("some\\
     thing")

something

I know this post is old, but I had a Situation like this and just want to share my solution. All the answers above work fine. But if you have a Code such as those in data.table chaining Syntax it becomes abit challenging. e.g. I had a Problem like this.

mass <- files[, Veg:=tstrsplit(files$file, "/")[1:4][[1]]][, Rain:=tstrsplit(files$file, "/")[1:4][[2]]][, Roughness:=tstrsplit(files$file, "/")[1:4][[3]]][, Geom:=tstrsplit(files$file, "/")[1:4][[4]]][time_[s]<=12000]

I tried most of the suggestions above and they didn´t work. but I figured out that they can be split after the comma within []. Splitting at ][ doesn´t work.

mass <- files[, Veg:=tstrsplit(files$file, "/")[1:4][[1]]][, 
    Rain:=tstrsplit(files$file, "/")[1:4][[2]]][, 
    Roughness:=tstrsplit(files$file, "/")[1:4][[3]]][, 
    Geom:=tstrsplit(files$file, "/")[1:4][[4]]][`time_[s]`<=12000]

This will keep the \n character, but you can also just wrap the quote in parentheses. Especially useful in RMarkdown.

t <- ("
this is a long
string
")

There is no coinvent way to do this because there is no operator in R to do string concatenation.

However, you can define a R Infix operator to do string concatenation:

`%+%` = function(x,y) return(paste0(x,y))

Then you can use it to concat strings, even break the code to multiple lines:

s = "a" %+%
    "b" %+%
    "c"

This will give you "abc".