create circular dot grids

I have the plot of the borders of the continents. how can i create circles like those in the picture? I have the latitude and longitude of the central point, the radius of the circumference, which would be a distance, and 10 points that would build the circumference that are 36 degrees apart from each other.

Answer 1

[Simon Chan]

Use function pol2cart

clear; clc;
separation = 36;                            % Angle separation
rhoA = 10;                                  % Radius #1, 10 pixels
rhoB = 15;                                  % Radius #2, 15 pixels
num_dot = 360/separation +1;                % Total number of points
theta = linspace(-pi,pi,num_dot);           % Theta separation
cx = 50;                                    % Your center point, x-coordinates = 50 (example)
cy = 25;                                    % Your center point, y-coordinates = 25 (example)
[xA,yA] = pol2cart(theta,rhoA);             % Use pol2cart
[xB,yB] = pol2cart(theta,rhoB);             % Use pol2cart
A = zeros(100,100);                         % Original region, example, size: 100x100
[Ny, Nx]= size(A);
xA_convert = round(cx-xA);                  % Convert back from polar coordinates
yA_convert = round(cy-yA);
xB_convert = round(cx-xB);
yB_convert = round(cy-yB);
for k = 1:num_dot
    A(yA_convert(k),xA_convert(k)) =1;      % Put the dots in matrix A (can skip this loop)
    A(yB_convert(k),xB_convert(k)) =1;
end
plot(cx,cy,'ro');                           % Your center point
hold on
plot(xA_convert,yA_convert,'b+')
plot(xB_convert,yB_convert,'g*')
xlim([0 Nx])
ylim([0 Ny])

[ELISABETTA BILLOTTA]

ok thanks now i try :)

[ELISABETTA BILLOTTA]

it seems to work but how do I convert the radius in pixels to km? in the sense I have the information of the distance in km, I have to enter the pixel from what I understand.

Thanksss

[Simon Chan]

May use this function: latlon2local