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iCAPs/packages/gspbox/graphs/gsp_two_moons.m
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gsp_two_moons.m
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function [G]=gsp_two_moons(sigmag,N,sigmad,d)
%GSP_TWO_MOONS Initialize a two moons graph
% Usage: G = gsp_two_moons(sigmag);
% G = gsp_two_moons(sigmag,N,sigmad);
% G = gsp_two_moons(sigmag,N,sigmad,d);
%
% Input parameters:
% sigmag: parameter for the construction of the graph (default 0.05)
% N : Number of vertices. (default 2000)
% sigmad: variance of the data
% d : distance of the two moons (default 0.5)
%
% Output parameters:
% G : Graph structure.
%
% Initialise the two moons graph. If less than 2 parameters are given, a standard
% graph is created. Otherwise, ....
%
% Example:
%
% G = gsp_two_moons();
% gsp_plot_signal(G,G.labels);
%
%
% Url: http://lts2research.epfl.ch/gsp/doc/graphs/gsp_two_moons.php
% Copyright (C) 2013-2016 Nathanael Perraudin, Johan Paratte, David I Shuman.
% This file is part of GSPbox version 0.7.0
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program. If not, see <http://www.gnu.org/licenses/>.
% If you use this toolbox please kindly cite
% N. Perraudin, J. Paratte, D. Shuman, V. Kalofolias, P. Vandergheynst,
% and D. K. Hammond. GSPBOX: A toolbox for signal processing on graphs.
% ArXiv e-prints, Aug. 2014.
% http://arxiv.org/abs/1408.5781
% Author : Nathanael Perraudin
if nargin < 1
sigmag = 0.05;
end
paramnn.sigma = sigmag;
paramnn.k = 5;
if nargin < 2
P = gsp_pointcloud('two_moons');
G = gsp_nn_graph(P,paramnn);
G.labels = (2*((1:G.N)>1000)-1)';
G.type = 'Two moons standard';
else
if nargin<4
d = 0.5;
end
N1 = floor(N/2);
N2 = N - N1;
% moon 1
phi1 = rand(N1,1) * pi;
r1 = 1;
rb = sigmad * randn(N1,1);
%rb = laprnd(N1, 1, 0, sigmad);
ab = rand(N1,1) * 2 * pi;
b = rb .*exp(1i.*ab);
bx = real(b);
by = imag(b);
moon1x = cos(phi1) .* r1 + 0.5 + bx;
moon1y = -sin(phi1) .* r1 + by-(d-1)/2;
% plot(moon1x , moon1y,'xb');
% moon 2
phi2 = rand(N2,1) * pi;
r2 = 1;
rb = sigmad * randn(N2,1);
ab = rand(N2,1) * 2 * pi;
b = rb .*exp(1i.*ab);
bx = real(b);
by = imag(b);
moon2x = cos(phi2) .* r2 - 0.5 + bx;
moon2y = sin(phi2) .* r2 + by+(d-1)/2;
% hold on;
% plot(moon2x , moon2y,'xr');
data = [moon1x,moon1y;moon2x,moon2y]';
G = gsp_nn_graph(data',paramnn);
G.labels = (2*((1:G.N)>N1)-1)';
G.type = 'Two moons synthetised';
end
end
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