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[Octave-bug-tracker] [bug #30400] bug of interp2 for small number of ele
From: |
Thorsten Meyer |
Subject: |
[Octave-bug-tracker] [bug #30400] bug of interp2 for small number of elements in xi and yi |
Date: |
Fri, 09 Jul 2010 18:34:41 +0000 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.10) Gecko/20100623 Iceweasel/3.5.10 (like Firefox/3.5.10) |
URL:
<http://savannah.gnu.org/bugs/?30400>
Summary: bug of interp2 for small number of elements in xi
and yi
Project: GNU Octave
Submitted by: tmeyier
Submitted on: Fri 09 Jul 2010 06:34:40 PM UTC
Category: Libraries
Severity: 3 - Normal
Item Group: Incorrect Result
Status: None
Assigned to: None
Originator Name: Thorsten Meyer
Originator Email:
Open/Closed: Open
Discussion Lock: Any
Release: dev
Operating System: GNU/Linux
_______________________________________________________
Details:
trying a few things in the context of bug #29601, I stumbled across the
following strange behaviour:
demo example 7 for interp2 looks like this:
A=[13,-1,12;5,4,3;1,6,2];
x=[0,1,2]; y=[10,11,12];
xi=linspace(min(x),max(x),17);
yi=linspace(min(y),max(y),26)';
mesh(xi,yi,interp2(x,y,A,xi,yi,'cubic'));
[x,y] = meshgrid(x,y);
hold on; plot3(x(:),y(:),A(:),"b*"); hold off;
It works nicely with the present tip. This is also ok:
octave:41> interp2(x,y,A,xi(1:8),yi(1:4),'cubic')
ans =
Columns 1 through 6:
13.000000 9.773438 6.968750 4.585938 2.625000 1.085938
12.212800 9.302787 6.770550 4.616087 2.839400 1.440488
11.451200 8.845838 6.575950 4.641537 3.042600 1.779138
10.715200 8.402587 6.384950 4.662287 3.234600 2.101888
Columns 7 and 8:
-0.031250 -0.726562
0.419350 -0.224012
0.851150 0.258638
1.264150 0.721388
I get a 4 by 8 matrix of interpolated values corresponding to a 4by8 field of
value pairs at which to interpolate.
But this is not good:
octave:42> interp2(x,y,A,xi(1:3),yi(1:4),'cubic')
error: bicubic: A(I,J,...) = X: dimensions mismatch
error: called from:
error: /home/thorsten/hg/octave/scripts/general/bicubic.m at line 186,
column 12
error: /home/thorsten/hg/octave/scripts/general/interp2.m at line 346,
column 12
And this is at least strange:
octave:42> interp2(x,y,A,xi(1),yi(1),'cubic')
ans =
13 13 13 13
Why don't I get only one value for one value pair to be interpolated?
_______________________________________________________
Reply to this item at:
<http://savannah.gnu.org/bugs/?30400>
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- [Octave-bug-tracker] [bug #30400] bug of interp2 for small number of elements in xi and yi,
Thorsten Meyer <=