You can control the marker positions on a line plot using the 'MarkerIndices' property. With that, you can specify at which indices of the data points you want to display markers.
For example, let us create 1000 points ranging from 0 to 10, and create a sinusoidal function of increasing amplitude.
x = linspace(0,10,1000);
y = exp(x/10).*sin(4*x);
Now, let us plot the function with a solid line and add asterisk markers every tenth data points:
plot(x,y,'-*','MarkerIndices',1:10:length(y))
The result is the following:
You can find more information about creating a line plot with markers here:https://www.mathworks.com/help/matlab/creating_plots/create-line-plot-with-markers.html
