[Octave-bug-tracker] [bug #31070] fzero cannot compute initial bracketing

[Carlo de Falco]

URL:
  <http://savannah.gnu.org/bugs/?31070>

                 Summary: fzero cannot compute initial bracketing
                 Project: GNU Octave
            Submitted by: cdf
            Submitted on: Sun 19 Sep 2010 02:24:28 PM CEST
                Category: Libraries
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  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:

with today's tip:

>> fun = @(x) x.^2 - 1 + exp(x); 
>> fzero (fun, 1)
ans = 0
>> fzero (fun, -1)
ans = 0
>> fzero (fun, 1.1)
error: fzero: not a valid initial bracketing
error: called from:
error:   /Users/carlo/Desktop/OF/octave/octave/fzero.m at line 170, column 5

as a reference, here are results from Matlab:

>> fun = @(x) (x.^2 - 1 + exp(x));
>> fzero (fun, 1)
ans =
   5.4422e-18
>> fzero (fun, 1.1)
ans =
  -1.3817e-17
>> fzero (fun, -1)
ans =
   -0.7146

the incorrect behavior is present in the 3.2.x release but
prior to 3.2 Octave was giving results more similar to Matlab.

c.




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