function plota_regra( x, y, regra, CORES )

figure
hold on
if nargin<4
    CORES = 'brgkym';
end
for qC = 1:length(CORES)
    plot( x(regra==qC), y(regra==qC), '.', ...
        'markersize', 1, 'color', CORES(qC) )
end