Change half of my plotted shape a different color

I made a star in mat lab using the corditnates

x = [0 7 4 10 3 0 -3 -10 -4 -7];
y = [0 -5 4 9 9 16 9 9 4 -5];

I then have it filled in, but is there a way to have the upper and lower halfs of the star be diferent colors. Right now i have it one solid color using the fill method.

[Mario Malic]

See patch function.

Answer 1

[Voss]

x = [0 7 4 10 3 0 -3 -10 -4 -7];
y = [0 -5 4 9 9 16 9 9 4 -5];

I shift the order of the points in x and y so the top part of the star is first and the bottom part is second:

x = circshift(x,-3)

x = 1×10

10 3 0 -3 -10 -4 -7 0 7 4

y = circshift(y,-3)

y = 1×10

9 9 16 9 9 4 -5 0 -5 4

(Of course, you could just redefine x and y:)

% x = [10 3  0 -3 -10 -4 -7 0  7 4];
% y = [ 9 9 16  9   9  4 -5 0 -5 4];

Define some "halfway" y-coordinate where the color will change:

y_half = 5.5; % change this to change where the "halfway" point is (anywhere from 4 to 9 will work)

Figure out the x-coordinates of the two points along the star whose y-coordinate is y_half:

x_half_left = interp1(y([end 1]),x([end 1]),y_half)

x_half_left = 5.8000

x_half_right = interp1(y(end/2+[0 1]),x(end/2+[0 1]),y_half)

x_half_right = -5.8000

Define two new pairs of vectors defining the top and bottom parts:

y_top = [y_half y(1:end/2) y_half];
y_bottom = [y_half y(end/2+1:end) y_half];
x_top = [x_half_left x(1:end/2) x_half_right];
x_bottom = [x_half_right x(end/2+1:end) x_half_left];

Create the patches (you could also create one patch with two faces if you want):

patch(x_top,y_top,'r')
patch(x_bottom,y_bottom,'g')