You can use the text function to put labels at x-y coordinates. Name-value pairs can be used to determine where to place the labels relative to the coordinates (e.g. left, right, centered, etc.).
text(x, y, ["my" "labels" "etc..."])
I'm not sure what you were trying to do with a, b, and c in the above code, or if you have a separate question about that.
-Cam
