Hi Vitalie,

thank you for the hint! Seems like I should finally learn dplyr and
change my coding style.

Sven


Am 06.05.19 um 13:25 schrieb Vitalie Spinu:

Hi Sven,

My suggestion would be that instead of cluttering your code with such "old
fashion" assignments you would switch to dplyr mutate or data.table's inline
:=. Both are the de-facto standards in the wild by now.

  Vitalie

On Tue, Apr 30 2019 15:28, Alex Branham via ESS-help wrote:

On Tue 30 Apr 2019 at 13:25, Sven Hartenstein via ESS-help 
<ess-help@r-project.org> wrote:

Dear ESS users and developers,

when writing R code to manipulate an object or data frame column, I
often find myself retyping the expression on the left side of "<-" as
some argument for a function call or assignment on the right side of
"<-".

Here are two examples. Imagine your point is at _POINT_ and you want to
insert 'data[,"columnA"]' in the first example and in the second example
'data[ data[,"columnB"] < 123 ,"columnA"]' at point.

data[,"columnA"] <- tolower(_POINT_)

data[ data[,"columnB"] > 123 ,"columnA"] <- gsub("xxx",
                                                   "yyy",
                                                   _POINT_,
                                                   fixed=TRUE)

Wouldn't it be handy to have a lisp function which copies the expression
on the left side of "<-" and inserts it at point?

Or is something like this already available in ESS?

Not to my knowledge, no.

What do you think?

I don't think it's a terrible idea; I've found myself wanting to do that
several times in the past (though less so now with magrittr pipes).

I guess implementation-wise the tricky bit would be figuring out what to
do in the case of 1) more than one assignment e.g. x <- y <- 2 and also
2) how to find the start of the "left" side. It would be tricky to
differentiate between:

x[[
   1]] <- 1

and

x <- 1
y <- 2

since we can't reliably detect complete R, especially not backwards. I
guess one quick workaround would be to work with indentation --- just to
take all the lines starting with whitespace before the <- until we find
one all-whitespace line or the first line that doesn't start with
whitespace.

Thanks for the suggestion,
Alex

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