circle marker weird filling

The circle marker is doing something weird. How can I fix this? Is it the edge thing or the order or what? How do I 'smooth' the edges? Is it because it is filled? It doesn't do it when it's not 'filled'? C2 is an RGB colour code.

plot(time,strain,'-o','Color',C2,'LineWidth',lw,'MarkerSize',ms,'MarkerEdgeColor',C2,'MarkerFaceColor',C2);

[Herline van der Spuy]

@Walter Roberson

I've got data till 100 seconds. I'll post the first 21s.

figure
% Temperature 22°C
% B22 is the data with time in first column and strain in second colomn.
time = B22(:,1);
strain = B22(:,2);
lw = 3;
ms = 7;
sz = 22;
C2 = [0.267 0.447 0.768];
plot(time,strain,'-o','Color',C2,'LineWidth',lw,'MarkerSize',ms,'MarkerEdgeColor',C2,'MarkerFaceColor',C2);

ax = gca;
set(gca,'fontsize',sz);
grid on
xlim([0 110]);
ylabel('Strain  (%)','FontSize',sz);
xlabel('Time  (s)','FontSize',sz);

[Walter Roberson]

When I try with my own system, or with MATLAB Online, the plot looks fine no matter how much I zoom. However, when I run it here with the MATLAB Answers facility, it does indeed look bad.

filename = 'https://www.mathworks.com/matlabcentral/answers/uploaded_files/777428/21seconds_time_strain.xlsx';
T = readtable(filename, 'VariableNamingRule', 'preserve');
B22 = [T.Time, T.Strain];

figure
% Temperature 22°C
% B22 is the data with time in first column and strain in second colomn.
time = B22(:,1);
strain = B22(:,2);
lw = 3;
ms = 7;
sz = 22;
C2 = [0.267 0.447 0.768];
plot(time,strain,'-o','Color',C2,'LineWidth',lw,'MarkerSize',ms,'MarkerEdgeColor',C2,'MarkerFaceColor',C2);

ax = gca;
set(gca,'fontsize',sz);
grid on
xlim([0 15]);
ylabel('Strain  (%)','FontSize',sz);
xlabel('Time  (s)','FontSize',sz);

[Herline van der Spuy]

Luckily, the figure is scale down a bit. And you can't see the difference on the pdf. So that's okay. But thank you for the help.

Answer 1

[Walter Roberson]

Linewidth problems. The circle is drawn as a series of straight segments and when the Linewidth is not 1 the ends of the lines extend out in a way that leaves the shape non-circular. The line segments are constant width, not feathered taking into account the line width.

[Herline van der Spuy]

Oh, that's interesting. So the circle is basicaly a * shape but with a lot of lines extending outward and with a line width of 1. How would I go about changing the marker linewidth and the actual line's line width? Aka how do I separate those? I know with scatter I can adjust the line width of the marker, but not sure how to do it with the plot.

[Walter Roberson]

I don't seem to be replicating the problem in my tests. Could you attach data to test with, including the values of lw and ms ?

Also, what shows up for

opengl info

[Kelly Kearney]

You can play around with layering separate line and marker objects to get a more aesthetically pleasing look:

lw = 5;
mksz = 8;

subplot(3,1,1);
plot(1:10, 1:10, '-bo', 'markersize', mksz, 'linewidth', lw, 'markeredgecolor', 'b', 'markerfacecolor', 'r');

% If you want a linewidth around the markers comparable to the line, layer
% edgeless markers of different sizes
subplot(3,1,2);
plot(1:10, 1:10, '-bo', 'markersize', mksz+lw, 'linewidth', lw, 'markeredgecolor', 'none', 'markerfacecolor', 'b');
hold on;
plot(1:10, 1:10, 'o', 'markersize', mksz-lw/2, 'markeredgecolor', 'none', 'markerfacecolor', 'r');

% If you're okay with a thinner marker outline, you can use markers with a
% different line width
subplot(3,1,3);
plot(1:10, 1:10, '-b', 'linewidth', lw);
hold on;
plot(1:10, 1:10, 'o', 'markersize', mksz, 'linewidth', 1, 'markeredgecolor', 'b', 'markerfacecolor', 'r');

(Note: the auto-generated Answers image is pretty low-res... it looks better when run in actual Matlab)

Answer 2

[Image Analyst]

Try a dot

plot(time,strain,'b.-','Color',C2,'LineWidth',lw,'MarkerSize',ms,'MarkerEdgeColor',C2,'MarkerFaceColor',C2);