James_H:

I looked over the docs, and the code looks reasonable. What problem are you having? Is the program not compiling, or does it give an unreasonable value, or some other problem?

I'm not really interested in installing the modules so I can try out your code, nor do I know what you want, nor do I know what it's giving you. If you add a bit more information to your post, someone may be able to help.

...roboticus

When your only tool is a hammer, all problems look like your thumb.