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wrong stock price data for backtesting

newbie so apologies for the basic question.

I am running zipline on my local machine and compare it with the result on Quantopian backtesting. Then I realized that the stock price differs between ( I am quite sure I am using the same time)

For example. AAPL price on Jan 7th 2013 was 70.30, but the web page shows 74.85 !!

The code are exactly the same, the only difference is
one is programmatically seting the start/end time, the other is to use Quantipian's UI to set time.
Really confused about that.

2 responses

How are you obtaining the historical quote? Perhaps you are using a different data source? As was explained to me just recently, Quantopian uses a data source which feeds them minute data, so it often does not match up with the "official" closing price.

I am using api load_from_yahoo, which should be yahoo! finance.

I find the thread talking about the difference data source. That might be the reason.

Thanks Eliot !