Great illustration of history function and statistical library.

Yet... One has to be careful when it comes to claiming a win over buy and hold. Quantopian S&P 500 benchmark does not re-invest dividends, thus over time almost any algorithm that occasionally sets the holding to 100% of SPY etf will beat the benchmark. This is the reason I have nudged the development team on several occasions to include and option for S&P 500 with re-invested dividends as a benchmark option.

Say that all algorithm does is keep the investment at 100% SPY. That means every few months a few new etf stocks will be bought, while the benchmark will be 5%, 10%, ... 50% in cash in 10 years or so. Towards the end the higher exposure to the index and zero return on dividend cash will tilt the result in algorithm's favor. That is not to say the algorithm does not make money, but that the test confirming it is invalid.

I have changed the algorithm to keep the position at 100% of s&p at the end of each day. As it turns out, it beats not only the benchmark but also the algorithm above. 41% return during the same period, vs. 33% for the original algorithm and 23.4% of s&p with no dividend re-invested. This is why the re-invested dividend s&p is such an important benchmark.

One may be able to beat the market, but it is much harder than it seems. Badly constructed benchmark leads to a wrong comparison, thus making it look easy.

The change to the benchmark being used is being tested. If it passes tests, it will ship this week. If it doesn't pass the tests. . . well then we'll have to see what it didn't pass and go from there.

Great information about the benchmarks. Thanks.

Thanks to good folk of Quntopian for responsiveness. Here's my updated wishlist, based on common issues found in algorithms posted.

1. S&P500 benchmark with re-invested dividend, as discussed above.
   
2. Other benchmark options, such as DJIA or optional ticker, so one can compare to DIA or Russel ETF's.
   
3. Limit borrowing to zero or some fixed percentage, so algorithms can be sand boxed as in real life
   
4. Open price of the day, close price of the previous day, yearly/all-time high/low and similar data would be useful. One can construct it but not always easily

Looks like #1 and #2 are to be addressed shortly, #3 should work well once connected to play or real IB account, #4 is left to be desired for.

The new history function should work easily to solve #4

Here is another sample using Bollinger Bands

Here is another using Keltner channels. One must calculate the channels yourself, using a moving average and the ATR. But this is trivial to do. There is not trading for this one. I had to add a round function to the record to make it work, but I'm not sure why.