[Octave-bug-tracker] [bug #31871] interp1 gives the wrong result for cubic interpolation

[Ben Abbott]

URL:
  <http://savannah.gnu.org/bugs/?31871>

                 Summary: interp1 gives the wrong result for cubic
interpolation
                 Project: GNU Octave
            Submitted by: bpabbott
            Submitted on: Mon 13 Dec 2010 09:53:49 PM EST
                Category: Interpreter
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: None
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Mac OS

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Details:

Simple example ...


x = [1:4, 10];
f = @(x) polyval ([0 1 1], x);
interp1 (x, f(x), x, "cubic")
ans =     2.0000     3.0000     4.0000     5.0000   291.0000
f(x)
ans =    2    3    4    5   11


I see the same result for 3.0.5 and the developer's sources.




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