R help - Mar 2006 - atan2(1,1i)

Hi

?atan2 says that atan2(y,x)=atan(y/x) for x and y numeric or complex  
vectors.

Well, I would expect atan2(1,1i) to be equal to atan(-1i), but

 > atan2(1,1i)
Error in atan2(y, x) : Non-numeric argument to mathematical function
 > R.version
                _
platform       powerpc-apple-darwin8.5.0
arch           powerpc
os             darwin8.5.0
system         powerpc, darwin8.5.0
status         alpha
major          2
minor          3.0
year           2006
month          03
day            27
svn rev        37590
language       R
version.string Version 2.3.0 alpha (2006-03-27 r37590)
 >




--
Robin Hankin
Uncertainty Analyst
National Oceanography Centre, Southampton
European Way, Southampton SO14 3ZH, UK
  tel  023-8059-7743

Try this:
> atan2(1+0i,1i)
[1] NaN-Infi

Ravi.
> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch [mailto:r-help-
> bounces at stat.math.ethz.ch] On Behalf Of Robin Hankin
> Sent: Tuesday, March 28, 2006 9:13 AM
> To: RHelp
> Subject: [R] atan2(1,1i)
> 
> Hi
> 
> ?atan2 says that atan2(y,x)=atan(y/x) for x and y numeric or complex
> vectors.
> 
> Well, I would expect atan2(1,1i) to be equal to atan(-1i), but
> 
>  > atan2(1,1i)
> Error in atan2(y, x) : Non-numeric argument to mathematical function
>  > R.version
>                 _
> platform       powerpc-apple-darwin8.5.0
> arch           powerpc
> os             darwin8.5.0
> system         powerpc, darwin8.5.0
> status         alpha
> major          2
> minor          3.0
> year           2006
> month          03
> day            27
> svn rev        37590
> language       R
> version.string Version 2.3.0 alpha (2006-03-27 r37590)
>  >
> 
> 
> 
> 
> --
> Robin Hankin
> Uncertainty Analyst
> National Oceanography Centre, Southampton
> European Way, Southampton SO14 3ZH, UK
>   tel  023-8059-7743
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-
> guide.html

Robin Hankin wrote:
> Hi
> 
> ?atan2 says that atan2(y,x)=atan(y/x) for x and y numeric or complex  
> vectors.
> 
> Well, I would expect atan2(1,1i) to be equal to atan(-1i), but
> 
>  > atan2(1,1i)
> Error in atan2(y, x) : Non-numeric argument to mathematical function
Ravi Varadhan pointed out that you need to make both arguments complex
to address the error message you obtained... but atan2 wasn't originally
designed for complex arguments. I suspect that what you really want is
to use the Arg function:

 > Arg(1/1i)
[1] -1.570796

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