Hi all. I am studying the collision of two solitons of the NLS equation. Actually I just want to plot out the exact solutions given in R.S.Johnson's book. (page 321, figure 4.4). I have used matlab to do this and produced the figure using exactly the same values for the parameters. However, the produced graph is a little bit different from that in R.S.Johnson's book during collision. I am wondering what's wrong. Is there any standard animation available in the internet for the collision of two NLS solitons? This sounds very standard, but I can hardly find any... Will you have any reference?