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Comment by greendestiny | Hacker News Reader

Looks cool, can I ask where you sourced the historical data from?

We're using Xignite's API right now. It's super-simple to integrate with.

Why did you choose that over something like Yahoo! Finance or Google?

yeah that caught us out - we found that even though the data is freely available from those sources, you're not allowed to include that data in a commercial app :-(

Oh really? That's interesting - does that apply even if it's not distributed with the commercial app? I'm sure I've used trading platforms before which use Yahoo...

Our understanding of the Yahoo/google T&Cs was that we couldn't aim to profit from their data (http://finance.yahoo.com/badges/tos). We may be being overcautious but we didn't want to risk getting into trouble ;-)

I've had a lot of problems with Yahoo not having complete historical data, especially on thinly traded or OTC stocks. I wouldn't recommend using their data in a production application.

They look pretty awesome. I had some mobile app idea a while ago but commercial data rates are just too scary, good luck with this app!

How far back does it go?

Xignite allows us to show the full historical data of an instrument, but because we're taking a lean approach at testing how people use it, we're limiting them to a few years.

Super interesting! Could you shed some light on to how much you are spending on the data? Is it in the hundreds, thousands or ten-thousands? Is it feasible for one person to bootstrap a website with Xignite?

That's useful to know. Is that daily data? Have you found it to be reliable? When I started testing moving-average based strategies, my blog post about it ended up being largely about data issues, from both Google and Yahoo finance: http://grahamstratton.org/straightornamental/entries/movinga... An extreme example was an opening value off by a factor of 100 on one day.

In my experience, even historical or realtime data from Reuters/Bloomberg/CQG can have serious errors such as that - every trading system should be sanity checking its market data!!

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