The importance of providing a small, working example of code that exhibits your problem has already been mentioned here by pryrt (who even gave a small, working example :). Such an example (along with input data, expected and actual output, and warning/error messages) can greatly help us to help you. Again, please see Short, Self-Contained, Correct Example.

And the process of composing an SSCCE can often lead you to understand the problem entirely on your own.