Adding new circle to plot at constant frequency

Hello,

I am trying to plot figures that have a circle inside it. I want to add a new circle to the figure at a constant frequency. let us say each 20 steps. For example, if I have 60 steps then I should have 60 figures. Figures from 1 to 20 will have one circle, figures from 21 to 40 will have 2 circles, and figures from 41 to 60 will have three circles. I did that in below code and it is working properly. However, I used if condition in my code. The problem if I will have 1000 steps this mean I need to use (1000/20= 50) if condition and that does not make sense. Is there any sufficient way to do that. This is an example.In my real case, I will have from step 1-20 circle moving at each step from step 21-40 I will have two circles moving and so on. I gave this example to make the situation easy. I have the location (x,y) for all steps stored in one matrix.

 function h = circle(x,y,r)
clc;
for i=1:60
figure
if i>=1 && i<20    
x=10;
r=0.4;
y=18;
axis ([0 20 0 20])
hold on
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;
h = plot(xunit, yunit);
hold off

 elseif i>=20 && i<40
x=10;
r=0.4;
y=14;
axis ([0 20 0 20])     
hold on
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y+2;
h = plot(xunit, yunit);
hold off
hold on
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;
h = plot(xunit, yunit);
hold off

 else i>=40 && i<60;
x=10;
r=0.4;
y=10;
axis ([0 20 0 20])
hold on
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y+4;
h = plot(xunit, yunit);
hold off
hold on
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y+2;
h = plot(xunit, yunit);
hold off
hold on
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;
h = plot(xunit, yunit);
hold off
end

 end
 end

Figures that I got is like

and

and

%

Answer 1

[Robert]

You should put your circle plotting code in a for loop and iterate from 0 to floor(i/20) (or the reverse).

function h = circle % (x,y,r) % shouldn't have these inputs if we don't use them

x = 10;
r = 0.4;
y = 18;
th = 0:pi/50:2*pi;
xunit = r * cos(th) + x;
yunit = r * sin(th) + y;

for ii=1:60 % using ii avoids confusion with complex numbers
  figure
  axis([0 20 0 20])
  for jj = floor(ii/20):-1:0 % backwards to keep colors same as in your example
    h = plot(xunit, yunit+2*(jj-1));
    hold on
  end
  hold off
end

end

[Ali Kareem]

Hi,

Thank you for your reply.

I run code but unfortunately, it does not gave me same results as above and it does not plot figures from 1 to 20

[Robert]

Whoops! floor(ii/20) returns 0 for ii in [0,19]. I should have added 1 or iterated down to zero. I've edited my answer.