Is there any difference between <- and =

Dear R-helpers:

I have a question related to <- and =.

I saw very experienced R programmers use = rather than <- quite
consistently.
However, I heard from others that do not use = but always stick to <- when
assigning valuese.

I personally like = because I was using Matabl, But, would like to receive
expert opinion to avoid potential trouble.

Use <- for assignment, and = for function arguments.  Then the 
difference between

  f( a = 3 )
  f( a <- 3 )

is clear, and you won't be surprised that a gets changed in the second 
case.  If you use = for assignment, the two lines above will be written as

  f( a = 3 )
  f( ( a = 3 ) )

and it is very easy to miss the crucial difference between them.

Duncan Murdoch

Many thanks in advance.

-Sean

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Dear R-helpers:

I have a question related to <- and =.

I saw very experienced R programmers use = rather than <- quite
consistently.
However, I heard from others that do not use = but always stick to <- when
assigning valuese.

I personally like = because I was using Matabl, But, would like to receive
expert opinion to avoid potential trouble.

Many thanks in advance.

-Sean

The short answer is that <- is used for assignment, and = is used to
associate function arguments with their values.  You can use = instead
of <- for assignment too (in most contexts), but the converse isn't
true.

I've provided more detail about when you can and can't exchange the
two operators (and some of the history about the operators themselves)
in this blog post:

http://blog.revolution-computing.com/2008/12/use-equals-or-arrow-for-assignment.html

# David Smith

David M Smith <david at revolution-computing.com>
Director of Community, REvolution Computing www.revolution-computing.com
Tel: +1 (206) 577-4778 x3203 (Seattle, USA)

Use <- for assignment, and = for function arguments.  Then the
difference between

 f( a = 3 )
 f( a <- 3 )

is clear, and you won't be surprised that a gets changed in the second
case.  If you use = for assignment, the two lines above will be
written as

 f( a = 3 )
 f( ( a = 3 ) )

and it is very easy to miss the crucial difference between them.

in fact, some recent posts show that things can go the other way round: 
people try to use <- for function arguments.  i think the following is
the most secure way if one really really has to do assignment in a
function call:

    f({a=3})

and if one keeps this convention, <- can be dropped altogether.

vQ

I think most people find it odd at first if they have always used "=" but
quickly you get use to it and nothing could be more clear. It is explicit.
It is active and provides a direction, a value goes into an object. The
equal sign for assignment is ambiguous. 

As an example 

 x = 3

we only know that the value 3 is assigned to the object x because by
convention a number cannot be an object, if not it could be read as the
object "3" taking the value "x" The expression literally states that they
are equal, yet you cannot assume that all instances of 3 are equal to x, so
it is an inaccurate expression. On the other hand,

3 -> x  or 
x <- 3  

is very clear. It makes no changes to "3" only to "x"  I've been reading
"Data Manipulation with R" and find the author's use of "=" for assignment
disturbing. You quickly get use to -> and will find after a short time that
you prefer it.

Dear R-helpers:

I have a question related to <- and =.

I saw very experienced R programmers use = rather than <- quite
consistently.
However, I heard from others that do not use = but always stick to <- when
assigning valuese.

I personally like = because I was using Matabl, But, would like to receive
expert opinion to avoid potential trouble.

Many thanks in advance.

-Sean

	[[alternative HTML version deleted]]

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

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