Re: polyfit hangs on inf input

[Jaroslav Hajek]

On Mon, Nov 3, 2008 at 9:05 PM, Dmitri A. Sergatskov
<address@hidden> wrote:
> On Mon, Nov 3, 2008 at 12:32 PM, Søren Hauberg <address@hidden> wrote:
>> man, 03 11 2008 kl. 12:11 -0600, skrev Dmitri A. Sergatskov:
>>> The following code seems to hang octave 3.0.2 (on Fedora 9 x86_64):
>>>
>>> xx=linspace(-1,1,11);
>>> yy=2*linspace(-1,1,11);
>>> xx(6)=Inf;
>>> polyfit(xx',yy',1)
>>>
>>> The problem seems to be with underlying x\y code.
>>> I do not know WWMD in this case, but hanging does not
>>> seem to be appropriate. Either bailing out with an error,
>>> or ignoring with a warning seem to be better options.
>>
>> With 3.1.51+ I get
>>
>> octave:4> polyfit(xx',yy',1)
>> ans =
>>
>>   NaN   NaN
>
> This appears to be the (unintended?) result of the code:
>
>  if (nargout > 2)
>    ## Normalized the x values.
>    mu = [mean(x), std(x)];
>    x = (x - mu(1)) / mu(2);
>  endif
>
> (std(x) returns NaN if x has Infs)
>
> x\y would still hang.
>

Can you please extract the precise values of x and y for which x\y hangs?

> Anyone can check what would matlab do in
> either case?
>
>>
>> Søren
>>
>>
>
> Dmitri.
> --
>
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-- 
RNDr. Jaroslav Hajek
computing expert
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz