# How can I print small circles?

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Caglar on 30 Oct 2018
Edited: Caglar on 1 Nov 2018
Problem I am trying to print small (diameter=0.02 cm etc) filled circles to pdf in exact size. I am able to print exact circles with a diameter of 2 cm, 1 cm, 0.5 cm, but when I try to go below ~0.04 cm, printed figure does not include all circles. Let me show you what I mean with some sample pictures. Note that all circles are separated by their diameter length to obtain a nice stack of them. First image shows the output of same code with d=1, second is d=0.5 and final one is d=0.02.
First two images are correct. In the last image, you can see the most circles are not printed. Circles are in correct size but only a few of them are printed. It had to look stacked like first two, but only in smaller circles.
Codes:
cm2pts=72/2.54; %cm to inch and inch to points = cm to points
ax.Units='points'; fig.Units='points';
height=cm2pts*220; % 'page' dimensions
width=cm2pts*150;
ax.XLim=([0 width]); ax.XLim=([0 height]);
diameter=0.02*cm2pts;
distance=diameter;
...
here is a loop that creates a x,y position vector for all dots
...
plot(ax,x,y, 'MarkerFaceColor','black','MarkerEdgeColor','none','Marker','o','LineStyle','none','MarkerSize',diameter);
set(ax,'xtick',[],'ytick',[]);
ax.Units='normalized'; ax.Position=[0 0 1 1]; ax.Units='points';
fig.PaperUnits='points';
fig.PaperPositionMode = 'manual';
fig.PaperPosition=[0 0 width height];
fig.PaperSize = [PaperPosition(3) PaperPosition(4)];
print(fig,'-painters','output.pdf','-dpdf')
Notes:
-I tried up scaling everything, thinking that I would downscale while printing but it still failed, may be its about ratio of circle to drawing dimensions.
-I hand checked x, y positions, they are correct
-I tried changing marker to '.' but '.' cannot be less than ~2.5 mms even if you give MarkerSize as eps.
-I tried rectangle but it cannot be vectorized therefor its slow and causes too much ram and file size.
-I tried setting figure position to real size, output did not change.
-Output file dimensions are correct in all cases.
-I tried scatter but I simply could not get the real size I wanted from scatter. It says S (marker area) is points^2 in docs for scatter but I could not get any size, for instance d=1cm with scatter circles.
-Behaviour is same on Matlab Online.

KSSV on 30 Oct 2018
Edited: KSSV on 30 Oct 2018
dx = 0.25 ; % spacing in x
dy = 0.25 ; % spacing in y
x = 0:dx:1 ;
y = 0:dy:1 ;
[X,Y] = meshgrid(x,y) ; % generate mesh
% draw circle
th = linspace(0,2*pi) ;
r = 0.1 ; % radius of circle
xc = r*cos(th) ; yc = r*sin(th) ;
figure
hold on
for i = 1:size(X,1)
for j = 1:size(X,2)
x = X(i,j)+xc ;
y = Y(i,j)+yc ;
patch(x,y,'b')
end
end
plot(X,Y,'.r')
Caglar on 31 Oct 2018
Edited: Caglar on 1 Nov 2018
Hello, as I said in the main post, plot does work for markersizes smaller than 0.04 cm. But when you try to print smaller dots, it skips most of the dots in output. Thats what I need help for.

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