[R] syntax for extending a line in a script??

[David Winsemius]

On Jan 12, 2011, at 5:46 PM, Mike Williamson wrote:

> Hello,
>
>    A hopefully simple question.  I use 'R' through emacs, but I  
> suspect the
> following would occur with any manner of text editor:
>
>   - my editor has a normally quite handy feature where it will
>   automatically indent to the appropriate level when I start a new  
> line.
>   However, this occasionally creates cases where there is no  
> friendly way to
>   break a long line of code into two lines which still function as one
>   command.  Therefore, I need a nice way to be able to flag 'R' to  
> know that
>   the code is continuing on the next line.  Let me explain via  
> example:

My practice is to use the opening of a paired code delimiter like "["  
or "(" at the end of a line as I have modified your code to show:
>
>        numericColumns <- names(listOfDataFrames[[myDF]][,columnsOI])[
>                            sapply(listOfDataFrames[[myDF]] 
> [,columnsOI],
>                                   is.numeric) ]
>
>    As you can see in this case, I would *like* for these 2 lines of  
> code to
> be read as 1 line, but since the "names(<blah>)" command is  
> sufficiently a
> command on its own, 'R' see this as a completed line of code.  I  
> could try
> to break it up at different points, but emacs (and other text  
> editors) takes
> a guess as to the most intelligent way to indent, so that if I were  
> to write
> something like:
>
>        numericColumns <- names(listOfDataFrames[[myDF]][,columnsOI])
> [sapply(
>                      listOfDataFrames[[myDF]][,columnsOI],  
> is.numeric) ]
>
>
> it would actually indent something more like this:
>
>        numericColumns <- names(listOfDataFrames[[myDF]][,columnsOI])
> [sapply(
>
> listOfDataFrames[[myDF]][,columnsOI], is.numeric) ]
>
>
> and as you can see, that doesn't help the issue of preventing the  
> code from
> wrapping around (and therefore doesn't help readability).  Is there  
> some
> simple way to flag that the next line is continuing?  Something like
> python's "\" at the end of a line?  I tried wrapping the whole thing  
> around
> curly braces { } but that didn't work, either.
>
>                                           Thanks!
>                                                   Mike
>
>
> "Telescopes and bathyscaphes and sonar probes of Scottish lakes,
> Tacoma Narrows bridge collapse explained with abstract phase-space  
> maps,
> Some x-ray slides, a music score, Minard's Napoleanic war:
> The most exciting frontier is charting what's already here."
>  -- xkcd
>
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David Winsemius, MD
West Hartford, CT