How "best" to allow a web-page visitor to construct mathematical or statistical tools?

I have a free web site that streams real-time stock-options data. I want to let users make and then save their own JavaScript-callable tools to interpret options data. Users can invoke these custom tools to help them make their own sell/buy decisions about options.

But I am totally stopped, stymied, dead-ended, and buffaloed as to how to accomplish this. If there were just a few choices, I guess开发者_运维知识库 I could stumble around blindfolded (as I am now) and finally hit on one that kind-of worked.

But the choices seem endless:

1. Let the user write JavaScript tools that I'd then interpret;
2. Mathematica and like toolsets;
3. Many statistics packages;
4. Google spreadsheet API.

And overwhelmingly many more.

If anyone has struggled through the process of giving a user some facility for making statistics and probability tools, how did you finally end up? And would you do it that way again?

Plus, my feature-creeposis and perfectionitis want me to integrate charts, graphs, heat maps, and who knows what else more; or at least to allow later integration of graphics.

Graphics would be nice and sexy: I'd like to drop everything and do graphics. But I have to resist and get something onto the page real soon now.¹

Q: What can/should I do to allow and encourage easy, intuitive, secure, and powerful tool construction?

EDIT: I definitely don't mean that I want to invent a whole new system de novo. I only (uh-huh, yeah, that's right; 'only' :-) want to interface with some already-existing JavaScript-callable package.

Thanks so much!

¹ Now I know a little bit of how my employers might have felt about me at one time: "aw, c'mahhhhhhhhhn, this feature is just too sexy to leave out."

If you need to get something out the door quickly, the first best stop-gap solution is to give people the ability to export their data to a tool they already know how to use (e.g., Excel) for exactly this purpose. Worry about your own version of the wheel once you've provided some basic short-term solution.

Of course, that's not to marginalize the topic of building a functional, browser-based statistical analysis package, which certainly seems interesting. But to be perfectly honest you might as well come to SO and post "Hey guys, I need to develop a new Operating System for the iPhone. Any ideas?" ;)