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[Octave-bug-tracker] [bug #32045] demo for mkpp throws an error.


From: Ben Abbott
Subject: [Octave-bug-tracker] [bug #32045] demo for mkpp throws an error.
Date: Tue, 04 Jan 2011 01:28:32 +0000
User-agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6_5; en-US) AppleWebKit/534.10 (KHTML, like Gecko) Chrome/8.0.552.231 Safari/534.10

URL:
  <http://savannah.gnu.org/bugs/?32045>

                 Summary: demo for mkpp throws an error.
                 Project: GNU Octave
            Submitted by: bpabbott
            Submitted on: Mon 03 Jan 2011 08:28:31 PM EST
                Category: Interpreter
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Incorrect Result
                  Status: None
             Assigned to: None
         Originator Name: Ben Abbott
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Mac OS

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Details:


octave:2> demo mkpp
mkpp example 1: # linear interpolation
 x=linspace(0,pi,5)'; 
 t=[sin(x),cos(x)];
 m=diff(t)./(x(2)-x(1)); 
 b=t(1:4,:);
 pp = mkpp(x, [m(:),b(:)]);
 xi=linspace(0,pi,50);
 plot(x,t,"x",xi,ppval(pp,xi));
 legend("control","interp");

mkpp example 1: failed
mkpp: num intervals in x doesn't match num polynomials in P


Comparing to Matlab, the fields for the piecewise polynominal (pp) are
different, but there is no error.


x = linspace (0, pi, 5)'; 
t = [sin(x), cos(x)];
m = diff (t) ./ (x(2) - x(1)); 
b = t(1:4,:);
pp = mkpp (x, [m(:), b(:)])

pp = 

      form: 'pp'
    breaks: [0 0.7854 1.5708 2.3562 3.1416]
     coefs: [4x4 double]
    pieces: 4
     order: 4
       dim: 1

pp.coefs

ans =

    0.9003   -0.3729         0    1.0000
    0.3729   -0.9003    0.7071    0.7071
   -0.3729   -0.9003    1.0000    0.0000
   -0.9003   -0.3729    0.7071   -0.7071






    _______________________________________________________

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  <http://savannah.gnu.org/bugs/?32045>

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