[R] R is GNU S, not C.... [was "how to get or store ....."]

[ronggui]

======= 2005-12-07 04:17:03 ÄúÔÚÀ´ÐÅÖÐÐ´µÀ£º=======

>From: vincent at 7d4.com
>> 
>> ronggui a écrit :
>> 
>> > I think it is NOT just for historical reason.
>> > see the following example:
>> > 
>> >>rm(x)
>> >>mean(x=1:10)
>> > [1] 5.5
>> >>x
>> > Error: object "x" not found
>> 
>> x is an argument local to mean(),
>> did you expect another answer ?
>> 
>> >>mean(x<-1:10)
>> > [1] 5.5
>> >>x
>> >  [1]  1  2  3  4  5  6  7  8  9 10
>> 
>> What is the goal of this "example" ?
>
>I believe it's to show why "<-" is to be preferred over "=" for
>assignment...

Yeah,I want to show "<-" is to be preferred.
Sorry for not making it clearly.

>> Here with "<-",
>> (voluntary, or not, side effect)
>> the global variable x is, also, created.
>> Did the writer really want that ???
>
>Very much so, I believe.
> 
>> I though there were other specific statements
>> especially intended for global assignment, eg "<<-".
>
>You need to distinguish assignment in function _call_ and assignment in
>function _definition_.  They ain't the same.
> 
>> If this example was intended to prove "<-"
>> is better than "="
>> ... I'm not really convinced !
>
>In that case, let's try another one (which is one big reason I stopped using
>"=" for assignment):
>
>
>> long.comp <- function(n) {
>+     Sys.sleep(n)
>+     n
>+ }
>> result = long.comp(30)
>> system.time(result = long.comp(30))
>Error in system.time(result = long.comp(30)) : 
>	unused argument(s) (result ...)
>> system.time(result <- long.comp(30))
>[1]  0.00  0.00 30.05    NA    NA
>> str(result)
> num 30
>
>Cheers,
>Andy
> 
>>
>
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= = = = = = = = = = = = = = = = = = = =
			


 

2005-12-07

------
Deparment of Sociology
Fudan University

My new mail addres is ronggui.huang at gmail.com
Blog:http://sociology.yculblog.com