bugGNU Octave - Bugs: bug #47013, bug in spline function

 
 

bug #47013: bug in spline function

Submitter:  None
Submitted:  Fri 29 Jan 2016 05:04:39 PM UTC
 
Category:  Octave Function Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Incorrect Result
Status:  Fixed Assigned to:  None
Originator Name:  bug in spline function Originator Email:  -email is unavailable-
Open/Closed:  * Closed Release:  * 4.0.0
Operating System:  * GNU/Linux
* Mandatory Fields

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Sat 20 Feb 2016 08:11:01 PM UTC, comment #5: 

I applied Lachlan's patch to stable (http://hg.savannah.gnu.org/hgweb/octave/rev/7a91166b1d09).  This should be a part of the 4.0.1 bug fix release.

Rik <rik5>
Project Administrator
Tue 16 Feb 2016 12:05:42 PM UTC, comment #4: 

I can confirm that the other cases do not also need the added .'(:).  The attached patch makes that clearer by removing some unnecessary code, which took (1:n-1,:) of vectors that were already row vectors.

The change in 138~139 seems unnecessary because of automatic broadcasting.

(file #36356)

Lachlan Andrew <lachlan>
Mon 15 Feb 2016 10:05:36 PM UTC, comment #3: 

Confirming that Marco's change fixes the reported problem and attaching as a diff (just to make clear which lines were changed). I can't say whether this change is appropriate or complete.

(file #36350)

Mike Miller <mtmiller>
Project Administrator
Mon 01 Feb 2016 08:44:02 AM UTC, comment #2: 

I confirm the problem and I was able to fix with the only change

d = d(1:n-1,:); d = d.'(:);
c = c(1:n-1,:); c = c.'(:);
b = b(1:n-1,:); b = b.'(:);
a = a(1:n-1,:); a = a.'(:);

Can you confirm?

Marco Caliari <caliari>
Project Member
Fri 29 Jan 2016 05:09:28 PM UTC, comment #1: 

Note:

I was trying to implement the example of MatLab function spline:

x = pi*[0:.5:2];
y = [0  1  0 -1  0  1  0;
     1  0  1  0 -1  0  1];
pp = spline(x,y);
yy = ppval(pp, linspace(0,2*pi,101));

It returned an error, and I tried to fix it.

This is my fixed source code.

ChingChuan Chen

Anonymous
Fri 29 Jan 2016 05:04:39 PM UTC, original submission:  

Hi,

There is a bug in spline.

For the complete case in function `spline`, when n > 2,

(line 138 ~ 139 in source code)

      g(2:n-1,:) = (a(3:n,:) - a(2:n-1,:)) ./ h(2:n-1) - ...
                   (a(2:n-1,:) - a(1:n-2,:)) ./ h(1:n-2);

should be

      g(2:n-1,:) = (a(3:n,:) - a(2:n-1,:)) ./ h(2:n-1, idx) - ...
                   (a(2:n-1,:) - a(1:n-2,:)) ./ h(1:n-2, idx);

and (line 147~150 in source code)

      d = d(1:n-1,:);
      c = c(1:n-1,:);
      b = b(1:n-1,:);
      a = a(1:n-1,:);

should be

      d = d(1:n-1,:); d = reshape(permute(d, [2, 1]), 1, []);
      c = c(1:n-1,:); c = reshape(permute(c, [2, 1]), 1, []);
      b = b(1:n-1,:); b = reshape(permute(b, [2, 1]), 1, []);
      a = a(1:n-1,:); a = reshape(permute(a, [2, 1]), 1, []);

sincerely,

ChingChuan Chen

Anonymous

 

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Attach Files:
   
   
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Attached Files
file #36356:  bug_47013.cset added by lachlan (2KiB - application/octet-stream)
file #36350:  spline.diff added by mtmiller (549B - text/x-diff)

 

Depends on the following items: None found

Items that depend on this one: None found

 

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  • -email is unavailable- added by rik5 (Posted a comment)
  • -email is unavailable- added by lachlan (Updated the item)
  • -email is unavailable- added by mtmiller (Updated the item)
  • -email is unavailable- added by caliari (Posted a comment)
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    Follow 7 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2016-02-20 rik5 StatusPatch Submitted Fixed
        Open/ClosedOpen Closed
    2016-02-16 lachlan Attached File- Added bug_47013.cset, #36356
    2016-02-15 mtmiller Attached File- Added spline.diff, #36350
        CategoryNone Octave Function
        StatusConfirmed Patch Submitted
    2016-02-01 caliari StatusNone Confirmed

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