posting/comment activity over time graph plugin

I’m searching for a plugin that will create a simple bar chart graph that shows posting and comment activity over a specified period of time. Over, say 1 month, or 1 year, or over the length of the blog.

I don’t need to distinguish between posts and comments, and particularly DON’T want them separated.

I’ve searched the statistics section of the plugin directory, but haven’t found what I’m looking for.

Any ideas?

Thanks

Keith