How to count the amount of markers in a figure?

Hello guys,

For my thesis I am trying to create a figure/picture with a X amount of Stars/Dots/... as i needed this in my experiment. I found a code that is kind of able to do this, but the amount of Stars/Dots is not exactly equal to the amount that if fill in the code. Not sure how to make sure that the amount of stars/dots is exactly equal to the amount I fill in. Thanks in advance!

The code I am using:

x = rand(1, 10000);
y = rand(1, 10000);
minAllowableDistance = 0.05;
numberOfPoints = 50;
% Initialize first point.
keeperX = x(1);
keeperY = y(1);
% Try dropping down more points.
counter = 2;
for k = 2 : numberOfPoints
  % Get a trial point.
  thisX = x(k);
  thisY = y(k);
  % See how far is is away from existing keeper points.
  distances = sqrt((thisX-keeperX).^2 + (thisY - keeperY).^2);
  minDistance = min(distances);
  if minDistance >= minAllowableDistance
    keeperX(counter) = thisX;
    keeperY(counter) = thisY;
    counter = counter + 1;
  end
end
plot(keeperX, keeperY, 'bx','MarkerSize',9);
axis([-0.1 1.1 -0.1 1.1]);

Answer 1

[KSSV]

x = rand(1, 10000);
y = rand(1, 10000);
minAllowableDistance = 0.05;
numberOfPoints = 50;
% Initialize first point.
keeperX = zeros([],1) ; 
keeperY = zeros([],1) ; 

keeperX(1) = x(1);
keeperY(1) = y(1);
% Try dropping down more points.
counter = 1;
for k = 2 : numberOfPoints
    % Get a trial point.
    thisX = x(k);
    thisY = y(k);
    % See how far is is away from existing keeper points.
    distances = sqrt((thisX-keeperX).^2 + (thisY - keeperY).^2);
    minDistance = min(distances);
    if minDistance >= minAllowableDistance
        counter = counter + 1;
        keeperX(counter) = thisX;
        keeperY(counter) = thisY;
        
    end
end
plot(keeperX, keeperY, 'bx','MarkerSize',9);
axis([-0.1 1.1 -0.1 1.1]);

[Nick de Groene]

If I run this code and then count the amount of stars, the amount of stars is not equal to numberOfPoints = 50

I used a counting program to count the dots. And also counted by hand to make sure.

See picture below

NumberOfPoints = 50 VS Count: 42

[KSSV]

Try this:

x = rand(1, 10000);
y = rand(1, 10000);
minAllowableDistance = 0.05;
numberOfPoints = 50;
% Initialize first point.
keeperX = zeros([],1) ;
keeperY = zeros([],1) ;

keeperX(1) = x(1);
keeperY(1) = y(1);
% Try dropping down more points.
counter = 1;
k = 0 ; 
while counter <= numberOfPoints-1
    k = k+1 ;
    % Get a trial point.
    thisX = x(k);
    thisY = y(k);
    % See how far is is away from existing keeper points.
    distances = sqrt((thisX-keeperX).^2 + (thisY - keeperY).^2);
    minDistance = min(distances);
    if minDistance >= minAllowableDistance
        counter = counter + 1;
        keeperX(counter) = thisX;
        keeperY(counter) = thisY;        
    end
end
plot(keeperX, keeperY, 'bx','MarkerSize',9);
axis([-0.1 1.1 -0.1 1.1]);

[Image Analyst]

After your loop, you can count the number of non-zero keeperX values.

indexes = keeperX > 0;
% Extract only the ones we want to plot.
keeperX = keeperX(indexes);
keeperY = keeperY(indexes);
fprintf('Number of points plotted = %d.\n', length(keeperX));
plot(keeperX, keeperY, 'bx','MarkerSize',9);

[Nick de Groene]

Thanks guys! This is really helpful!