Hello, I'm a newbie on matlab.

I am trying to find the value houghpeaks and I try to use the source code on Gonzales' book. But what came out was always

' Attempted to access nhood(2); index out of bounds Because numel(nhood)=1. '

How do I resolve this problem? Thanks

` function [r, c, hnew] = houghpeaks(h, numpeaks, threshold, nhood) %HOUGHPEAKS Detect peaks in Hough transform.`

% [R, C, HNEW] = HOUGHPEAKS(H, NUMPEAKS, THRESHOLD, NHOOD) detects

% peaks in the Hough transform matrix H. NUMPEAKS specifies the

% maximum number of peak locations to look for. Values of H below

% THRESHOLD will not be considered to be peaks. NHOOD is a

% two-element vector specifying the size of the suppression

% neighborhood. This is the neighborhood around each peak that is

% set to zero after the peak is identified. The elements of NHOOD

% must be positive, odd integers. R and C are the row and column

% coordinates of the identified peaks. HNEW is the Hough transform

% with peak neighborhood suppressed.

%

% If NHOOD is omitted, it defaults to the smallest odd values >=

% size(H)/50. If THRESHOLD is omitted, it defaults to

% 0.5*max(H(:)). If NUMPEAKS is omitted, it defaults to 1.

% Copyright 2002-2004 R. C. Gonzalez, R. E. Woods, & S. L. Eddins

% Digital Image Processing Using MATLAB, Prentice-Hall, 2004

% $Revision: 1.5 $ $Date: 2003/11/21 13:34:50 $

if nargin < 4 nhood = size(h)/50; % Make sure the neighborhood size is odd.

nhood = max(2*ceil(nhood/2) + 1, 1); end if nargin < 3 threshold = 0.5 * max(h(:)); end if nargin < 2 numpeaks = 1; end done = false; hnew = h; r = []; c = []; while ~done [p, q] = find(hnew == max(hnew(:))); p = p(1); q = q(1); if hnew(p, q) >= threshold r(end + 1) = p; c(end + 1) = q; % Suppress this maximum and its close neighbors.

p1 = p - (nhood(1) - 1)/2; p2 = p + (nhood(1) - 1)/2; q1 = q - (nhood(2) - 1)/2; q2 = q + (nhood(2) - 1)/2; [pp, qq] = ndgrid(p1:p2,q1:q2); pp = pp(:); qq = qq(:); % Throw away neighbor coordinates that are out of bounds in

% the rho direction.

badrho = find((pp < 1) | (pp > size(h, 1))); pp(badrho) = []; qq(badrho) = []; % For coordinates that are out of bounds in the theta

% direction, we want to consider that H is antisymmetric

% along the rho axis for theta = +/- 90 degrees.

theta_too_low = find(qq < 1); qq(theta_too_low) = size(h, 2) + qq(theta_too_low); pp(theta_too_low) = size(h, 1) - pp(theta_too_low) + 1; theta_too_high = find(qq > size(h, 2)); qq(theta_too_high) = qq(theta_too_high) - size(h, 2); pp(theta_too_high) = size(h, 1) - pp(theta_too_high) + 1; % Convert to linear indices to zero out all the values.

hnew(sub2ind(size(hnew), pp, qq)) = 0; done = length(r) == numpeaks; else done = true; end end

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