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Re: Re: A new version of bicubic in Octave


From: Hoxide Ma
Subject: Re: Re: A new version of bicubic in Octave
Date: Fri, 2 Sep 2005 22:26:00 +0800 (CST)

Thank you for you to notice me this bug.
it's not only a mistake in typeing. It's a big
mistake, 
I have read the interp2.m especially the part of
'linear', then fixed the bug in bicubic.m .

now follow codes work well:

   A=[13,-1,12;5,4,3;1,6,2];
   x=[0,1,4]+10; y=[-10,-9,-8];
   xi=linspace(min(x),max(x),17);
   yi=linspace(min(y),max(y),26);
   mesh(xi,yi,bicubic(x,y,A,xi,yi));
   [x,y] = meshgrid(x,y);
   __gnuplot_raw__ ("set nohidden3d;\n")
   hold on; plot3(x(:),y(:),A(:),"b*"); hold off;


but :
   ...
   mesh(xi,yi,interp2(x,y,A,xi,yi,'cubic'));
   ... 

have a problem.

you see the end of yi value is be eated :$

I will try to fix this problem. 
In fact, the reason is that Y is negative, then Y *
(1+eps) < Y, it's an expection. In my bicubic code , i
fixed this bug by move all points into positive part.


I attach the new version of bicubic.m


--- Paul Kienzle <address@hidden>写道:

> Fixed bug in line:
> 
>     t = 1 + (YI-Y(1))./((Y(rz)-Y(1))/(rz-1));
> 
> One of the Y was an X.
> 
> 
> Doesn't work for X non-uniform.  E.g.:
> 
>   A=[13,-1,12;5,4,3;1,6,2];
>   x=[0,1,4]+10; y=[-10,-9,-8];
>   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);
>   __gnuplot_raw__ ("set nohidden3d;\n")
>   hold on; plot3(x(:),y(:),A(:),"b*"); hold off;
> 
> - Paul
> 
> 
> On Aug 28, 2005, at 9:43 AM, Hoxide Ma wrote:
> 
> > It's really a new version , not based on any
> commerce
> > codes.
> >
> > It's based on my note:
> >
> > http://wiki.woodpecker.org.cn/moin/Octave/Bicubic?
> 
> > action=AttachFile&do=get&target=bicubic.pdf
> >
> > You can test my code by run intt1.m and intt2.m .
> >
> > intt2.m is a example to interpolation  by a
> > anomalistic surface.
> >
> > BTW: I'm sorry for my poor English :P
> >
> >
>
==========================================================
> >
> > A student of Math in Soochow University in China.
> > Intrested in Math, Python, Octave, Lisp, Maxima,
> Prolog and .NET/MONO.
> >
> > Blog: http://blog.sina.com.cn/blog/1142604745
> > Wiki: http://wiki.woodpecker.org.cn/moin/Hoxide
> >
> >
> >     
> >
> >     
> >             
> >
>
___________________________________________________________
> > 雅虎免费G邮箱-中国第一绝无垃圾邮件骚扰超大邮箱
> > http://cn.mail.yahoo.com
> > <interp2.m><intt1.m><intt2.m><bicubic.m>
> 
> 

==========================================================

A student of Math in Soochow University in China.
Intrested in Math, Python, Octave, Lisp, Maxima, Prolog and .NET/MONO.

Blog: http://blog.sina.com.cn/blog/1142604745
Wiki: http://wiki.woodpecker.org.cn/moin/Hoxide


                
___________________________________________________________ 
雅虎免费G邮箱-No.1的防毒防垃圾超大邮箱 
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Attachment: bicubic.m
Description: pat1535429516


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