If I understand correctly, C -- the type of each cell -- identifies the corresponding quadrant for each point. You also want to show each type in the diagram. Here's a script to do this using a different fill color for each cell type:
load test_data % load X and Y (data in script posted in question)
% compute C to identify each cell as S, L, or R, as in question
S = X >= 0 & Y >= 0;
L = X > 0 & Y < 0;
R = X < 0 & Y > 0;
C = 0*S + 1*L + 2*R;
% get voronoi verticies (v) and cells (c) for data set
[v, c] = voronoin([X Y]);
% create basic voronoi figure from data in question
voronoi(X,Y);
axis([-4.1 4.1 -4 4]);
% color the cells to show type
hold on;
for i=1:length(X)
% get verticies of next polygon
px = v(c{i},1);
py = v(c{i},2);
% choose a color, as per cell type
switch C(i)
case 0
clr = [.9 .8 .7]; % S
case 1
clr = [.7 .8 .9]; % L
case 2
clr = [.8 .7 .9]; % R
end
% fill the polygon to show cell type
fill(px, py, clr, 'FaceAlpha', 0.5);
end
