Matlab plots are grainy

I am using Matlab 2018b. The plots are grainy. Looks like drawn by chalk. I have used the following lines of code:

subplot(1,4,3)

plot(time2, final_l, 'Linewidth', 2);
grid on
ylim([0 0.45])
xlim([0 8])
xlabel('Time (s)')
ylabel('Mean value (uS)')
title('Lower Riddle')

And the resulting figures are like this:

How do I make the plots smooth?

[Nicolas B.]

It looks strange. Have you still the same effect with different linewidth? (e.g. 1, 3, 4, 5...)

Could you please get the object returned by the plot() function and upload here its values.

To get the object:

subplot(1,4,3)
h = plot(time2, final_l, 'Linewidth', 2);
grid on
ylim([0 0.45])
xlim([0 8])
xlabel('Time (s)')
ylabel('Mean value (uS)')
title('Lower Riddle')

and you can directly in a post here write down all properties of h.

[Walter Roberson]

What shows up for

openGL info

Also see https://blogs.mathworks.com/graphics/2015/07/13/graphicssmoothing-and-alignvertexcenters/