Re: extrapolate forbidden with interp1, spline

[David Bateman]

Eric Chassande-Mottin wrote:
> hi,
>
> I just wanted to mention that  the extrapolation
> (of a point outside the support of the input data set)
> is *not* allowed using interp1() with opt "spline" in GNU
> Octave, while it is in the corporate world.
>
> see:
>
> octave:1> interp1([1 2 3 4],[1 2 3 4],-1,'spline')
> ans = NA
>
> interp1 is the user-defined function from the file
> /usr/share/octave/2.9.14/m/general/interp1.m
>
>   
>>> interp1([1 2 3 4],[1 2 3 4],-1,'spline')
>>>       
>
> ans =
>
>     -1
>
> perhaps the way to solve this incompatibility
> is to invite the use of the 'extrap' opt with a warning
>
> octave:22> interp1([1 2 3 4],[1 2 3 4],-1,'extrap')
> ans = -1
>
>   
This is a bug in matlab, as extrapolation should only be done if the
"extrap" flag is given..

D.

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