How can I set an equal distance of 5 units between the red star points?

Hello everybody... I want to set an equal and fixed distance(5 units) between red star points in the whole figure(the three circles) in my attached code... How can I do it?? Please help me.Thanks in advance:)

Answer 1

[Image Analyst]

You can set up points at equal angles using code in the FAQ. http://matlab.wikia.com/wiki/FAQ#How_do_I_create_a_circle.3F However if you want the angles to be such that the arc length between the points is exactly 5 then the first and last point, near 0 and 2*pi, may not have an arc length of 5 between them unless the circumference is a multiple of 5. So it won't work for any arbitrary radius. If a spacing of 5 for nearly all pairs of points except for one pair is good enough for you, then see the 5th code chunk in the FAQ.

[Zeinab Ahmadi93]

Thanks for your reply dear... I read the references but unfortunately I still have problem I don't know how to code it.Can you help me to code it if you have time?

I want the distance between the markers on the circumference be equal to 5 units. for example for the circle with radius of 50 we have:

circumference= 2*pi*r~~2*3.14*50~~314

And we have 314/5= 62.8 ~ 63 markers on the circle.

[Image Analyst]

This will do it, but take note, that like I said, the first and last points may not be spaced exactly 5 apart:

% Initialization steps.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 20;

r1 = 50;
r2 = 35;
r3=  20;
xc = 50;
yc = 50;
% Since arclength = radius * (angle in radians),
% (angle in radians) = arclength / radius = 5 / radius.
deltaAngle1 = 5 / r1;
deltaAngle2 = 5 / r2;
deltaAngle3 = 5 / r3;
theta1 = 0 : deltaAngle1 : (2 * pi);
theta2 = 0 : deltaAngle2 : (2 * pi);
theta3 = 0 : deltaAngle3 : (2 * pi);
x1 = r1*cos(theta1) + xc;
y1 = r1*sin(theta1) + yc;
x2 = r2*cos(theta2) + xc;
y2 = r2*sin(theta2) + yc;
x3 = r3*cos(theta3) + xc;
y3 = r3*sin(theta3) + yc;
plot(x1,y1,'b')
hold on
plot(x2,y2,'b')
hold on
plot(x3,y3,'b')
hold on
grid on;

% Connecting Line:
plot([70 100], [50 50],'b','Marker','*','MarkerEdgeColor','r')
% Set up figure properties:
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0, 0, 1, 1]);
% Get rid of tool bar and pulldown menus that are along top of figure.
% set(gcf, 'Toolbar', 'none', 'Menu', 'none');
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 
drawnow;
axis square;

for i = 1 : length(theta1)
  plot(x1(i),y1(i),'r*')
  pause(0.1)
end
for i = 1 : length(theta2)
  plot(x2(i),y2(i),'r*')
  pause(0.1)
end
for i = 1 : length(theta3)
  plot(x3(i),y3(i),'r*')
  pause(0.1)
end

[Zeinab Ahmadi93]

Hello dear Image Analyst, I need your help and I will appreciate your help if you guide me when you have time... I am trying to do the same thing on Hexagon trajectory, But I don't know how to move a star marker on hexagons!

[Image Analyst]

The formula for a hexagon is not so simple as s=r*theta like it is for a circle. Sorry but I won't have time to help you with the trig formulas and if statements to do that.

[Walter Roberson]

interparc() can interpolate along hexagons, provided it is given the vertices.

Answer 2

[Walter Roberson]

You cannot get equal distance of 5 units on the circumference of a circle unless the units are fractions of 2*pi. However if the units are fractions of 2*pi then you cannot get equal distances on the straight line that also has red markers.

[Zeinab Ahmadi93]

Thanks for your reply dear Walter Roberson... But How did the writer of an article do it? This is the figure in that article:How can I change my code to generate an image like it because as you see the markers on the first circle are closer than others in my code.

[Walter Roberson]

You should probably look at https://www.mathworks.com/matlabcentral/fileexchange/34874-interparc