Provide more flexible holdouts for train-test extraction about lenskit

Merged in LingfeiH/lenskit (pull request #89, closes #33)

Add method and class to support the retain-N protocol

→ <<cset 86d5dbf711fa>>

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Created by @elehack on 2013-03-05T18:29:43.398723+00:00, last updated: None

There are two pieces to this:

• add a setRetain(int) method to CrossfoldCommand that sets up a retain-N partition
• create a new partition class, or extend CountPartition, to support the retain-N protocol

I think it is probably best to rename CountPartition to LastNPartition, and create a FirstNPartition to implement the new logic. These classes are not part of the public interface, so it is fine to reimplement them.

We should probably also improve the JavaDoc for setHoldout and setRetain to be clear, and create a new setHoldoutFraction method (and deprecate setHoldout(double)) to make things all clear.

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Created by @elehack on 2013-02-28T20:44:39.674033+00:00, last updated: None

Reducing scope to remove overlap with #205.

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Created by @elehack on 2013-02-05T23:06:38.018883+00:00, last updated: None

Michael Ekstrand [email protected] on 2011-10-18 13:55:03 said:

In [29e4320947109e148b63e35624964c80254f5179]:

Support fractional holdouts (refs #33).

* Re-implement holdout system in terms of orders and partition methods
* Add fractional holdout & parse percentages in config file

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Created by grouplens on 2013-02-01T21:55:29.835406+00:00, last updated: None

ekstrand on 2011-05-24 18:10:18 said:

We now do leave-N-out. We still need more flexibility, but it's a start.

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Created by grouplens on 2013-02-01T21:55:29.462014+00:00, last updated: None