How to change size and color of only some edges of a patch?

How can I change size/thikness and color of only some edges of a patch?

For example, here I would like to change size/thikness and color of non-consecutive edges:

x = [0 1 1 0];
y = [0 0 1 1];
patch(x,y,'red','FaceAlpha',0.2);

Answer 1

[Voss]

There are a couple of options for the 'EdgeColor' of a patch object that may work, e.g., use 'EdgeColor' 'flat' to have each edge's color match the color of a vertex, or 'interp' to have edge colors linearly vary along the edge according the colors at the beginning and end vertices.

However, I don't think there is a way to vary the thickness ('LineWidth') of different edges in a patch.

Therefore it may be necessary (or just easier) to set the patch's 'EdgeColor' to 'none' and create line objects on top of the patch along the patch's edges and the lines can be whatever color and thickness you want.

For example:

x = [0 1 1 0];
y = [0 0 1 1];
patch(x,y,'red','FaceAlpha',0.2,'LineStyle','none');

x_aug = x([1:end 1]);
y_aug = y([1:end 1]);
for ii = 1:numel(x_aug)-1
    line(x_aug(ii+[0 1]),y_aug(ii+[0 1]),'Color',rand(1,3),'LineWidth',randi(5));
end

You could even have many different lines running along an edge, one after the other, each with different properties:

figure();

x = [0 1 1 0];
y = [0 0 1 1];
patch(x,y,'red','FaceAlpha',0.2,'LineStyle','none');

x_aug = x([1:end 1]);
y_aug = y([1:end 1]);
N_segments = [1 5 10 20];
for ii = 1:numel(x_aug)-1
    x_temp = linspace(x_aug(ii),x_aug(ii+1),N_segments(ii)+1);
    y_temp = linspace(y_aug(ii),y_aug(ii+1),N_segments(ii)+1);
    for jj = 1:N_segments(ii)
        line(x_temp(jj+[0 1]),y_temp(jj+[0 1]),'Color',rand(1,3),'LineWidth',randi(5));
    end
end

[Sim]

Thanks a lot for your nice explanation! Very informative and useful!

[Sim]

Another solution just using plot:

x = [0 1 1 0];
y = [0 0 1 1];
hold on
patch(x,y,'red','FaceAlpha',0.2,'LineStyle','none');
plot(x(2:3),y(2:3),'r','linewidth',3)
hold off