Ideally, you would construct a reproducible example using one of R's many built-in datasets, or using synthetic data you generated yourself. At the very least, though, can you share the code you are running and the output that's causing trouble? It's very difficult to understand code problems from a prose description.
For instance, in this case I'm not sure if the above bit means that you are getting a specific error message, or if it means that the plot somehow doesn't look the way you want it to — or something else entirely?