Hello Beau,

Welcome! Some questions/comments:

1. Please clarify what you mean by "returns." Are you wanting to analyze price movements, with a positive daily return for a given security being an appreciation in price from the close of one day to the close of the next (or from open to close of the same day)? Or are you looking to establish positions in securities (long/short) and then rank the performance of each security? Also, if you are establishing positions, would you only consider realized returns, after closing out positions?
   
2. If you are interested in a "universe of stocks" I suggest having a look at the set_universe functionality described on the Quantopian help page (although at this point, to keep things simple, you might start with a short, fixed list of securities).
   
3. The Python coding seems pretty straightforward. Are you familiar with MATLAB? If so, Python numpy is very similar (e.g. see http://wiki.scipy.org/NumPy_for_Matlab_Users).
   
4. You can use the batch transform described on the Quantopian help page to accumulate a trailing window of daily OHLCV data.

Grant

Hi Grant, thanks for the reply and link. I haven't used Matlab since college but this is helpful nonetheless...

I'm looking to make the calculation on price movements, "with a positive daily return for a given security being an appreciation in price from the close of one day to the close of the next". Stated another way, I want to look at the changes in close price over the last 100 days and count the number of days where that change is less than the most recent change.

Seems easy enough to do with a loop of some sort, but I want to be most efficient since I'm going to be using a universe of stocks. And I kinda figured this would go into a batch transform but wanted to verify that as well...

Thanks,
Beau

Hello Beau,

Yes, the batch transform should do the trick. I've attached an example. It returns the prices in the columns of a numpy ndarray. The columns are ordered by sid in the list context.stocks. You can use numpy to compute the differences, do the counting, etc.

I don't have time now to work on an example...give it a go and post here if you get stuck.

Grant

Hello Beau,

I made a little headway. I think that I now have a row vector that contains the ranking you are looking for (not yet normalized). The next steps sorta depend on what you want to do. Are you looking to trade based on the info., or something else?

Grant

Thanks Grant, I think I understand it although how do I then reference a particular stock in the returned rank list? I'm using a loop to loop through a universe of stocks to issue orders so need to be able to pull out the corresponding rank for my signal calculation

Thanks,
Beau

Is it possible to use the ta lib rsi within a batch_transform?

Beau,

Glad that you're getting a feel for things.

I expect that there is a canned function in numpy that will allow you to do a sort/rank and also provide an array of the original indices. For example, if the original array of values is [5 7 2 4], then in ascending order, the array would be [2 4 5 7] with corresponding original indices 2, 3, 0, 1.

Regarding TA-Lib RSI with the batch transform, the answer is yes, it can be done as an unsupported hack. However, you might want to wait until some new functionality gets released described on https://github.com/quantopian/quantopian-drafts/blob/master/data-history-draft.md and discussed on https://www.quantopian.com/posts/draft-proposal-of-new-data-history-api.

Grant

The proposal looks much more intuitive and easy to use. Wonder how long it will take to release...

Hi,

In the ensuing 2 years since the last post in this thread, we've launched history and (more recently) pipeline. Attached is a backtest showing the metric described by the original poster using pipeline. I rank all securities with that factor and build a long/short portfolio with the top 100 vs the bottom 100.

happy coding,
fawce