If you're just trying to create a simple line plot (basically, connect a couple of points with straight lines) use the plot function. The documentation for the plot function, which you can access using the doc function, includes a simple example.
doc plot
I'm not quite sure I understand how you want to create a plot when you have more y coordinates for your points than you have x. Suppose I said I wanted to create a plot using dots where the three dots are at x coordinates 1, 2, and 3 and y coordinates 1 and 4. Your first question would probably be either "Do you mean three dots or just two?" or "What's the y coordinate of the third point?"
