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| author | VinceShieh <vincent.xie@intel.com> | 2016-09-21 10:20:57 +0100 |
|---|---|---|
| committer | Sean Owen <sowen@cloudera.com> | 2016-09-21 10:20:57 +0100 |
| commit | 57dc326bd00cf0a49da971e9c573c48ae28acaa2 (patch) | |
| tree | 3e57f59b33e42beddd1df72dbd85266e7b09ef7f /docs/ml-features.md | |
| parent | b366f18496e1ce8bd20fe58a0245ef7d91819a03 (diff) | |
| download | spark-57dc326bd00cf0a49da971e9c573c48ae28acaa2.tar.gz spark-57dc326bd00cf0a49da971e9c573c48ae28acaa2.tar.bz2 spark-57dc326bd00cf0a49da971e9c573c48ae28acaa2.zip | |
[SPARK-17219][ML] Add NaN value handling in Bucketizer
## What changes were proposed in this pull request?
This PR fixes an issue when Bucketizer is called to handle a dataset containing NaN value.
Sometimes, null value might also be useful to users, so in these cases, Bucketizer should
reserve one extra bucket for NaN values, instead of throwing an illegal exception.
Before:
```
Bucketizer.transform on NaN value threw an illegal exception.
```
After:
```
NaN values will be grouped in an extra bucket.
```
## How was this patch tested?
New test cases added in `BucketizerSuite`.
Signed-off-by: VinceShieh <vincent.xieintel.com>
Author: VinceShieh <vincent.xie@intel.com>
Closes #14858 from VinceShieh/spark-17219.
Diffstat (limited to 'docs/ml-features.md')
| -rw-r--r-- | docs/ml-features.md | 6 |
1 files changed, 5 insertions, 1 deletions
diff --git a/docs/ml-features.md b/docs/ml-features.md index 746593fb9e..a39b31c8f7 100644 --- a/docs/ml-features.md +++ b/docs/ml-features.md @@ -1102,7 +1102,11 @@ for more details on the API. ## QuantileDiscretizer `QuantileDiscretizer` takes a column with continuous features and outputs a column with binned -categorical features. The number of bins is set by the `numBuckets` parameter. +categorical features. The number of bins is set by the `numBuckets` parameter. It is possible +that the number of buckets used will be less than this value, for example, if there are too few +distinct values of the input to create enough distinct quantiles. Note also that NaN values are +handled specially and placed into their own bucket. For example, if 4 buckets are used, then +non-NaN data will be put into buckets[0-3], but NaNs will be counted in a special bucket[4]. The bin ranges are chosen using an approximate algorithm (see the documentation for [approxQuantile](api/scala/index.html#org.apache.spark.sql.DataFrameStatFunctions) for a detailed description). The precision of the approximation can be controlled with the |