function [b] =  bookfig3(a)
% Simple script to generate Figure 3, chapter 14 WITHOUT SPM! Just Matlab
% Book: Human Brain Function. Academic Press, 2nd edition, 2003
% Authors: Frackowiak, Friston, Frith, Dolan, Price, Zeki, Ashburner, and Penny.
% Script source: http://www.poirrier.be/~jean-etienne/presentations/rft/

% !!!!! YOU SHOULD HAVE RUN SCRIPT bookfig1.m BEFORE THIS ONE
% !!!!!!!!!! IN ORDER TO HAVE THE CORRECT AND SAME 'a' MATRIX !

% How to run it? "z3 = bookfig3(z);"
% Argument 'a' is the square ramdom map from script bookfig1!

% Requires: Image Processing Toolbox for fspecial() and conv2()

% Clear screen
clf;
close;

% Compute the "Gaussian filter" - It's not really the one used in the book!
hsize = 100; % will use a Gaussian filter with this hsize
FWHM = 3; % full width at half maximum
sigma = FWHM / sqrt(8*log(2)); % fspecial() needs sigma and not FWHM
%sigma = 1.2;
G = fspecial('gaussian', hsize, sigma);

% Apply filter to matrix a -becomes-> b
b = conv2(G, a, 'same');

% Rescale map to match 0.0 -> 1.0
maxi = max(max(b))
for i = 1:hsize
    for j = 1:hsize
        b(i,j) = b(i,j) / maxi;
    end
end
meany = mean(mean(b))

% Now display b, the filtered matrix
h = imagesc(b);

% Beautify image
set(gca,'YDir','normal');
colormap(gray);
ylabel('Position du pixel en Y');
xlabel('Position du pixel en X');