# ML: difference between partition\_field\_name and by\_field\_name in a population job? **URL:** \ **Category:** Elasticsearch\ **Tags:** elastic-stack-machine-learning\ **Created:** [October 27, 2021, 12:04pm UTC](https://discuss.elastic.co/t/ml-difference-between-partition-field-name-and-by-field-name-in-a-population-job/287792 "2021-10-27T12:04:42Z")\ **Posts on this page:** 1\ **Showing post:** 2
**Author:** ![richcollier](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/richcollier/32/115035_2.png) [@richcollier](https://discuss.elastic.co/u/richcollier)\ **Post date:** [October 27, 2021, 1:59pm UTC](https://discuss.elastic.co/t/ml-difference-between-partition-field-name-and-by-field-name-in-a-population-job/287792/2 "2021-10-27T13:59:28Z")
The role of a population job is NOT to detect new entities in a population - it is to detect entities behaving differently from their peers . If you want something like detecting new entities, then choose a temporal (non-population) job and choose `by_field` as the split (Relevant: [ML Kibana: difference between by\_field\_name and partition\_field\_name](https://discuss.elastic.co/t/ml-kibana-difference-between-by-field-name-and-partition-field-name/193385) and my comment on the notion of "dawn of time") Also relevant: [Temporal vs. Population Analysis in Elastic Machine Learning | Elastic Blog](https://www.elastic.co/blog/temporal-vs-population-analysis-in-elastic-machine-learning) Alternatively, if you want to detect something novel, you can consider using the `rare` function. See : [Dec 4th, 2018: [EN][ML] Rarity Analysis with Machine Learning](https://discuss.elastic.co/t/dec-4th-2018-en-ml-rarity-analysis-with-machine-learning/158979) --- _[View the full topic](https://discuss.elastic.co/t/ml-difference-between-partition-field-name-and-by-field-name-in-a-population-job/287792)._