From aea676ca2d07c72b1a752e9308c961118e5bfc3c Mon Sep 17 00:00:00 2001 From: BenFradet Date: Fri, 11 Dec 2015 15:43:00 -0800 Subject: [PATCH] [SPARK-12217][ML] Document invalid handling for StringIndexer Added a paragraph regarding StringIndexer#setHandleInvalid to the ml-features documentation. I wonder if I should also add a snippet to the code example, input welcome. Author: BenFradet Closes #10257 from BenFradet/SPARK-12217. --- docs/ml-features.md | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/docs/ml-features.md b/docs/ml-features.md index 6494fed0a01e5..8b00cc652dc7a 100644 --- a/docs/ml-features.md +++ b/docs/ml-features.md @@ -459,6 +459,42 @@ column, we should get the following: "a" gets index `0` because it is the most frequent, followed by "c" with index `1` and "b" with index `2`. +Additionaly, there are two strategies regarding how `StringIndexer` will handle +unseen labels when you have fit a `StringIndexer` on one dataset and then use it +to transform another: + +- throw an exception (which is the default) +- skip the row containing the unseen label entirely + +**Examples** + +Let's go back to our previous example but this time reuse our previously defined +`StringIndexer` on the following dataset: + +~~~~ + id | category +----|---------- + 0 | a + 1 | b + 2 | c + 3 | d +~~~~ + +If you've not set how `StringIndexer` handles unseen labels or set it to +"error", an exception will be thrown. +However, if you had called `setHandleInvalid("skip")`, the following dataset +will be generated: + +~~~~ + id | category | categoryIndex +----|----------|--------------- + 0 | a | 0.0 + 1 | b | 2.0 + 2 | c | 1.0 +~~~~ + +Notice that the row containing "d" does not appear. +