[Scilab-users] [EXTERNAL] Re: acos leads to complex values

[Stéphane Mottelet]

It is the same if x is slightly > 1:

--> x=1+%eps
  x  =

    1.


--> acos(x)
  ans  =

    2.107D-08i

--> format(25); x
  x  =

    1.0000000000000002220446

Le 29/01/2019 à 16:55, Carrico, Paul a écrit :
>
> When I scroll to the list, the lowest (positive) value is 8.4^E -08 
> (works fine) and no %eps .
>
> How Can I check if %eps is in?
>
> *De :*users [mailto:users-bounces at lists.scilab.org] *De la part de* 
> Stéphane Mottelet
> *Envoyé :* mardi 29 janvier 2019 16:50
> *À :* users at lists.scilab.org
> *Objet :* [EXTERNAL] Re: [Scilab-users] acos leads to complex values
>
> Le 29/01/2019 à 16:45, Carrico, Paul a écrit :
>
>     Dear All
>
>     I spent some time in looking for a mistake in my code ; finally
>     I’ve found that the ACOS of a real vector leads to some complex
>     values (???)
>
>     acos(Scar_P(:,1)./CM_x_CN(:,1))
>
> Are your really sure, because we may have
>
> --> x=-1-%eps
>  x  =
>
>   -1.
>
>
> --> acos(x)
>  ans  =
>
>    3.1415927 - 2.107D-08i
>
> S.
>
>     (the formula worked so far)
>
>     I checked that the input values are correct:
>
>     -Comprised between [-1; 1] using MIN and MAX
>
>     -Composed only of real values using ISREAL (all the vectors are
>     correct)
>
>     Thus I do not understand why complex values appear ?
>
>     May it come from the vectorization ?
>
>     Paul
>
>
>
>     _______________________________________________
>
>     users mailing list
>
>     users at lists.scilab.org  <mailto:users at lists.scilab.org>
>
>     https://antispam.utc.fr/proxy/1/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/lists.scilab.org/mailman/listinfo/users  <https://antispam.utc.fr/proxy/2/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/urldefense.proofpoint.com/v2/url?u=https-3A__antispam.utc.fr_proxy_1_c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy_lists.scilab.org_mailman_listinfo_users&d=DwMG-g&c=0hKVUfnuoBozYN8UvxPA-w&r=4TCz--8bXfJhZZvIxJAemAJyz7Vfx78XvgYu3LN7eLo&m=rN8DsnGalih7CBHModSb9evOi3rmZRFFYcBFHTC71gU&s=RgKyyESZ7uSTxlU7V0nR42XTJybjC0Ar5fDcrouQThE&e=>
>
> -- 
> Stéphane Mottelet
> Ingénieur de recherche
> EA 4297 Transformations Intégrées de la Matière Renouvelable
> Département Génie des Procédés Industriels
> Sorbonne Universités - Université de Technologie de Compiègne
> CS 60319, 60203 Compiègne cedex
> Tel : +33(0)344234688
> http://www.utc.fr/~mottelet  <https://antispam.utc.fr/proxy/2/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/urldefense.proofpoint.com/v2/url?u=http-3A__www.utc.fr_-7Emottelet&d=DwMG-g&c=0hKVUfnuoBozYN8UvxPA-w&r=4TCz--8bXfJhZZvIxJAemAJyz7Vfx78XvgYu3LN7eLo&m=rN8DsnGalih7CBHModSb9evOi3rmZRFFYcBFHTC71gU&s=34gC0H3RYWxwcKp7fr4bR5XFfy1acxO72YI9AYJJFhA&e=>
>
> _______________________________________________
> users mailing list
> users at lists.scilab.org
> https://antispam.utc.fr/proxy/1/c3RlcGhhbmUubW90dGVsZXRAdXRjLmZy/lists.scilab.org/mailman/listinfo/users


-- 
Stéphane Mottelet
Ingénieur de recherche
EA 4297 Transformations Intégrées de la Matière Renouvelable
Département Génie des Procédés Industriels
Sorbonne Universités - Université de Technologie de Compiègne
CS 60319, 60203 Compiègne cedex
Tel : +33(0)344234688
http://www.utc.fr/~mottelet

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.scilab.org/pipermail/users/attachments/20190129/9295c05c/attachment.htm>