Boxcount in a DEM ALOS image
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Hello. I am trying to make the boxcount in a satellite image (DEM ALOS) and this was the result:
Error using logical
NaN values cannot be converted to logicals.
Error in boxcount (line 64)
c = logical(squeeze(c));
Error in Alos_clip01 (line 6)
boxcount(c)
c = imread('Alos_clip01.tif');
imagesc(c)
colormap gray
axis square
%%
boxcount(c)
%%
[n, r] = boxcount(c);
loglog(r, n,'bo-', r, (r/r(end)).^(-2), 'r--')
xlabel('r')
ylabel('n(r)')
legend('actual box-count','space-filling box-count');
%%
boxcount(c, 'slope')
Boxcount code:
function [n,r] = boxcount(c,varargin)
%BOXCOUNT Box-Counting of a D-dimensional array (with D=1,2,3).
% [N, R] = BOXCOUNT(C), where C is a D-dimensional array (with D=1,2,3),
% counts the number N of D-dimensional boxes of size R needed to cover
% the nonzero elements of C. The box sizes are powers of two, i.e.,
% R = 1, 2, 4 ... 2^P, where P is the smallest integer such that
% MAX(SIZE(C)) <= 2^P. If the sizes of C over each dimension are smaller
% than 2^P, C is padded with zeros to size 2^P over each dimension (e.g.,
% a 320-by-200 image is padded to 512-by-512). The output vectors N and R
% are of size P+1. For a RGB color image (m-by-n-by-3 array), a summation
% over the 3 RGB planes is done first.
%
% The Box-counting method is useful to determine fractal properties of a
% 1D segment, a 2D image or a 3D array. If C is a fractal set, with
% fractal dimension DF < D, then N scales as R^(-DF). DF is known as the
% Minkowski-Bouligand dimension, or Kolmogorov capacity, or Kolmogorov
% dimension, or simply box-counting dimension.
%
% BOXCOUNT(C,'plot') also shows the log-log plot of N as a function of R
% (if no output argument, this option is selected by default).
%
% BOXCOUNT(C,'slope') also shows the semi-log plot of the local slope
% DF = - dlnN/dlnR as a function of R. If DF is contant in a certain
% range of R, then DF is the fractal dimension of the set C. The
% derivative is computed as a 2nd order finite difference (see GRADIENT).
%
% The execution time depends on the sizes of C. It is fastest for powers
% of two over each dimension.
%
% Examples:
%
% % Plots the box-count of a vector containing randomly-distributed
% % 0 and 1. This set is not fractal: one has N = R^-2 at large R,
% % and N = cste at small R.
% c = (rand(1,2048)<0.2);
% boxcount(c);
%
% % Plots the box-count and the fractal dimension of a 2D fractal set
% % of size 512^2 (obtained by RANDCANTOR), with fractal dimension
% % DF = 2 + log(P) / log(2) = 1.68 (with P=0.8).
% c = randcantor(0.8, 512, 2);
% boxcount(c);
% figure, boxcount(c, 'slope');
%
% F. Moisy
% Revision: 2.10, Date: 2008/07/09
% History:
% 2006/11/22: v2.00, joined into a single file boxcountn (n=1,2,3).
% 2008/07/09: v2.10, minor improvements
% control input argument
narginchk(1,2);
% check for true color image (m-by-n-by-3 array)
if ndims(c)==3
if size(c,3)==3 && size(c,1)>=8 && size(c,2)>=8
c = sum(c,3);
end
end
warning off
c = logical(squeeze(c));
warning on
dim = ndims(c); % dim is 2 for a vector or a matrix, 3 for a cube
if dim>3
error('Maximum dimension is 3.');
end
% transpose the vector to a 1-by-n vector
if length(c)==numel(c)
dim=1;
if size(c,1)~=1
c = c';
end
end
width = max(size(c)); % largest size of the box
p = log(width)/log(2); % nbre of generations
% remap the array if the sizes are not all equal,
% or if they are not power of two
% (this slows down the computation!)
if p~=round(p) || any(size(c)~=width)
p = ceil(p);
width = 2^p;
switch dim
case 1
mz = zeros(1,width);
mz(1:length(c)) = c;
c = mz;
case 2
mz = zeros(width, width);
mz(1:size(c,1), 1:size(c,2)) = c;
c = mz;
case 3
mz = zeros(width, width, width);
mz(1:size(c,1), 1:size(c,2), 1:size(c,3)) = c;
c = mz;
end
end
n=zeros(1,p+1); % pre-allocate the number of box of size r
switch dim
case 1 %------------------- 1D boxcount ---------------------%
n(p+1) = sum(c);
for g=(p-1):-1:0
siz = 2^(p-g);
siz2 = round(siz/2);
for i=1:siz:(width-siz+1)
c(i) = ( c(i) || c(i+siz2));
end
n(g+1) = sum(c(1:siz:(width-siz+1)));
end
case 2 %------------------- 2D boxcount ---------------------%
n(p+1) = sum(c(:));
for g=(p-1):-1:0
siz = 2^(p-g);
siz2 = round(siz/2);
for i=1:siz:(width-siz+1)
for j=1:siz:(width-siz+1)
c(i,j) = ( c(i,j) || c(i+siz2,j) || c(i,j+siz2) || c(i+siz2,j+siz2) );
end
end
n(g+1) = sum(sum(c(1:siz:(width-siz+1),1:siz:(width-siz+1))));
end
case 3 %------------------- 3D boxcount ---------------------%
n(p+1) = sum(c(:));
for g=(p-1):-1:0
siz = 2^(p-g);
siz2 = round(siz/2);
for i=1:siz:(width-siz+1)
for j=1:siz:(width-siz+1)
for k=1:siz:(width-siz+1)
c(i,j,k)=( c(i,j,k) || c(i+siz2,j,k) || c(i,j+siz2,k) ...
|| c(i+siz2,j+siz2,k) || c(i,j,k+siz2) || c(i+siz2,j,k+siz2) ...
|| c(i,j+siz2,k+siz2) || c(i+siz2,j+siz2,k+siz2));
end
end
end
n(g+1) = sum(sum(sum(c(1:siz:(width-siz+1),1:siz:(width-siz+1),1:siz:(width-siz+1)))));
end
end
n = n(end:-1:1);
r = 2.^(0:p); % box size (1, 2, 4, 8...)
if any(strncmpi(varargin,'slope',1))
s=-gradient(log(n))./gradient(log(r));
semilogx(r, s, 's-');
ylim([0 dim]);
xlabel('r, box size'); ylabel('- d ln n / d ln r, local dimension');
title([num2str(dim) 'D box-count']);
elseif nargout==0 || any(strncmpi(varargin,'plot',1))
loglog(r,n,'s-');
xlabel('r, box size'); ylabel('n(r), number of boxes');
title([num2str(dim) 'D box-count']);
end
if nargout==0
clear r n
end
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