How can I have a better plot?

I'm using codes given below in my program, but nodes which are plotted each loop are too small (maybe just one pixel). How can I bold nodes in my plot?

    figure(408)
    plot(S*step,Sigma{NodesR}(3),color)   
    hold on

Answer 1

[David Sanchez]

Change the marker size to fit your needs:

plot(rand(10), '*','MarkerSize',10)
plot(rand(10), '*','MarkerSize',5)