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Re: beginner: function definition confusion

From: Doug Stewart
Subject: Re: beginner: function definition confusion
Date: Thu, 21 Apr 2005 20:56:13 -0500
User-agent: Mozilla Thunderbird 1.0 (Windows/20041206)

Jeff Abrahamson wrote:

I'm confused trying to use nlfilter.  (The ultimate goal is to do
convolutions on images.)  I'm not sure if I'm misunderstanding
nlfilter or if I'm even maybe just defining the function avg
incorrectly.  Here's what I wrote

   function T1 ( )
     img = imread("black-white.png");
     blur = nlfilter(img,[3,3],avg)

blur = nlfilter(img,[3,3],avg(you must put something here)  )


   function ret = avg ( blk )
     ret = 0;
     for i = 1:3
        for j = 1:3
          ret += blk(i,j);
     ret /= 9;


The error is this:
 octave:1> T1()
 error: `blk' undefined near line 22 column 14
 error: evaluating assignment expression near line 22, column 11
 error: evaluating for command near line 21, column 5
 error: evaluating for command near line 20, column 3

Anyone see what I'm doing wrong?

Note, by contrast, that avg works in the form I thought I needed it

 octave:1> m=rand(3)
 m =

   0.30486  0.74804  0.28817
   0.54096  0.62247  0.70384
   0.67811  0.58588  0.38752

 octave:2> avg(m)
 ans = 0.53998
Thanks in advance.

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