Change color of points if the coordinates are the same

Hi, I'm new

I'm doing a simulation with Matlab and I like to change the color of a point when it have the same coordinate.

I have a matrix with all the 'x' and 'y' coordinates of all points and my program is plotting them one by one. I like to change the color when a point overlaps a other, so that I can see the density of points on this place.

Per example:

-All the plotted points are blue. (a lot)

-The coordinate of a single point is (1,1) => blue (this is ok)

- When a second plotted point have the same coordinate (1,1) it have to change in red

-When a third point passes throught the same coordinate (1,1) it have to change in yellow etc..

Do you have any ideas?

Thank you

Answer 1

[darova]

Look on this idea

• create matrix

• round data (snap to grid)

Fill matrix like

for i = 1:100
    A(y(i),x(i)) = A(y(i),x(i)) + 1;
end

The matrix will show density

[Johnny]

Thank you for this idea!

The problem is, I have a lot of points and it becomes unclear when they are adjacent.

Is there a way to find, in a matrix, the same coordinate (x and y) ? If this is possible, a new matrix can be plotted with these points in another color..

[darova]

Can you attach the data?

[Johnny]

nb_rotations = pi/2;

v_pl = 3;
v1 = 30;
v2 = v1;

R0 = 152;
R1 = 80;
R2 = 27.5;
R3 = 7.5;

d1=304/4;
d2=50;
d3=19;

theta1 = 0;%sup
dtheta1 = 1/200;

theta2 = 0;%ga
dtheta2 = 1/200;

theta3 = 0;%pel
dtheta3 = 1/200;

alpha=deg2rad(72);

angle = linspace(0,2*pi,200);  

[line3x,line3y] = pol2cart(angle,R3);

plot(line0x,line0y);

while (theta1 < nb_rotations)
%%%%%%%%%%%%    Calculations
    x1 = d1*cos(theta1);
    y1 = d1*sin(theta1);

    x2 = x1+d2*cos(theta2);
    y2 = y1+d2*sin(theta2);
     
    x3 = line3x+x2+d3*cos(theta3);
    y3 = line3y+y2+d3*sin(theta3);

%%%%%%%%%%%%%%%  Loops
hold all
pause(0.001);
theta1 = theta1 + dtheta1*v_pl;
theta2 = theta2 + dtheta2*v1;
theta3 = theta3 + dtheta3*v2;

%%%%%%%%%%%%%  Plots
plot(x3,y3,'b');


%%%%%%%%%%%%%  Axes
axis([-160 160 -160 160]); 
axis equal
grid on

end

[Johnny]

This is the code. If one cercle overlay another, it have to change the color at this point

Answer 2

[darova]

Here are some recommendations:

Add these lines into your code

Add these lines at the end of your code

xx = xx(:);         % make column
yy = yy(:);
xx = (xx-min(xx))/(max(xx)-min(xx))*98+1;   % scale data between 1..99
yy = (yy-min(yy))/(max(yy)-min(yy))*98+1;
xx = round(xx);     % round data
yy = round(yy);

A = zeros(100);     % preallocation

for i = 1:length(xx)
    A(yy(i),xx(i)) = A(yy(i),xx(i)) + 1;        % fill matrix
end

imagesc(A)

[Johnny]

This looks pretty good!! Thank you very much