R help - Apr 2005 - Inf +1i vs 1+Inf*1i

Hi

If I have

a <- Inf + 1i

then

Re(a) is Inf, and Im(a) is 1, as expected.

But if

b <- 1 + Inf * 1i,

then

Im(b) = Inf ,  as expected,   but Re(b) = NaN, which I didn't expect.


Why this asymmetry?   How to define an object with Re(b)=1, Im(b)=Inf?


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

Robin,

You could try

b <- complex(real=1, im=Inf)



------------------------------------------
?scar Manuel Rueda Palacio
Viceintervenci?n
Consejer?a de Hacienda 
Junta de Castilla y Le?n
Tfno: 983414092   e-mail: ruepalos at jcyl.es
------------------------------------------

-----Mensaje original-----
De: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch]En nombre de Robin Hankin
Enviado el: mi?rcoles, 13 de abril de 2005 9:51
Para: R-help at stat.math.ethz.ch
Asunto: [R] Inf +1i vs 1+Inf*1i


Hi

If I have

a <- Inf + 1i

then

Re(a) is Inf, and Im(a) is 1, as expected.

But if

b <- 1 + Inf * 1i,

then

Im(b) = Inf ,  as expected,   but Re(b) = NaN, which I didn't expect.


Why this asymmetry?   How to define an object with Re(b)=1, Im(b)=Inf?


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

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>>>>> "Robin" == Robin Hankin <r.hankin at
soc.soton.ac.uk>
>>>>>     on Wed, 13 Apr 2005 08:51:19 +0100 writes:
    Robin> Hi
    Robin> If I have

    Robin> a <- Inf + 1i

    Robin> then

    Robin> Re(a) is Inf, and Im(a) is 1, as expected.

    Robin> But if

    Robin> b <- 1 + Inf * 1i,

    Robin> then

    Robin> Im(b) = Inf ,  as expected,   but Re(b) = NaN, which I didn't
expect.

    Robin> Why this asymmetry?

I think this is a (very long standing) buglet in our complex
arithmetic, since you can directly see

  > 1+ 1i*Inf
  [1] NaN+Infi

    Robin> How to define an object with Re(b)=1, Im(b)=Inf?

{Oscar already mentioned    b <- complex(real=1, im=Inf) }

Martin Maechler, ETH Zurich