| = Analytics Reduction Functions |
| :toclevels: 2 |
| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you under the Apache License, Version 2.0 (the |
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| // with the License. You may obtain a copy of the License at |
| // |
| // http://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, |
| // software distributed under the License is distributed on an |
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| // KIND, either express or implied. See the License for the |
| // specific language governing permissions and limitations |
| // under the License. |
| |
| Reduction functions reduce the values of <<analytics-expression-sources.adoc#,sources>> |
| and/or unreduced <<analytics-mapping-functions.adoc#,mapping functions>> |
| for every Solr Document to a single value. |
| |
| Below is a list of all reduction functions provided by the Analytics Component. |
| These can be combined using mapping functions to implement more complex functionality. |
| |
| == Counting Reductions |
| |
| === Count |
| The number of existing values for an expression. For single-valued expressions, this is equivalent to `docCount`. |
| If no expression is given, the number of matching documents is returned. |
| |
| `count()` \=> `< _Single Long_ >` |
| `count(< T >)` \=> `< _Single Long_ >` |
| |
| === Doc Count |
| The number of documents for which an expression has existing values. For single-valued expressions, this is equivalent to `count`. |
| If no expression is given, the number of matching documents is returned. |
| |
| `doc_count()` \=> `< _Single Long_ >` |
| |
| `doc_count(< T >)` \=> `< _Single Long_ >` |
| |
| === Missing |
| The number of documents for which an expression has no existing value. |
| |
| `missing(< T >)` \=> `< _Single Long_ >` |
| |
| [[analytics-unique]] |
| === Unique |
| The number of unique values for an expression. This function accepts `Numeric`, `Date` and `String` expressions. |
| |
| `unique(< T >)` \=> `< _Single Long_ >` |
| |
| == Math Reductions |
| |
| === Sum |
| Returns the sum of all values for the expression. |
| |
| `sum(< _Double_ >)` \=> `< _Single Double_ >` |
| |
| === Variance |
| Returns the variance of all values for the expression. |
| |
| `variance(< _Double_ >)` \=> `< _Single Double_ >` |
| |
| === Standard Deviation |
| Returns the standard deviation of all values for the expression. |
| |
| `stddev(< _Double_ >)` \=> `< _Single Double_ >` |
| |
| === Mean |
| Returns the arithmetic mean of all values for the expression. |
| |
| `mean(< _Double_ >)` \=> `< _Single Double_ >` |
| |
| === Weighted Mean |
| Returns the arithmetic mean of all values for the second expression weighted by the values of the first expression. |
| |
| `wmean(< _Double_ >, < _Double_ >)` \=> `< _Single Double_ >` |
| |
| NOTE: The expressions must satisfy the rules for `mult` function parameters. |
| |
| == Ordering Reductions |
| |
| === Minimum |
| Returns the minimum value for the expression. This function accepts `Numeric`, `Date` and `String` expressions. |
| |
| `min(< T >)` \=> `< _Single_ T >` |
| |
| === Maximum |
| Returns the maximum value for the expression. This function accepts `Numeric`, `Date` and `String` expressions. |
| |
| `max(< T >)` \=> `< _Single_ T >` |
| |
| === Median |
| Returns the median of all values for the expression. This function accepts `Numeric` and `Date` expressions. |
| |
| `median(< T >)` \=> `< _Single_ T >` |
| |
| === Percentile |
| Calculates the given percentile of all values for the expression. |
| This function accepts `Numeric`, `Date` and `String` expressions for the 2^nd^ parameter. |
| |
| The percentile, given as the 1^st^ parameter, must be a <<analytics-expression-sources.adoc#numeric,constant double>> between [0, 100). |
| |
| `percentile(<Constant Double>, < T >)` \=> `< _Single_ T >` |
| |
| === Ordinal |
| Calculates the given ordinal of all values for the expression. |
| This function accepts `Numeric`, `Date` and `String` expressions for the 2^nd^ parameter. |
| The ordinal, given as the 1^st^ parameter, must be a <<analytics-expression-sources.adoc#numeric,constant integer>>. |
| *0 is not accepted as an ordinal value.* |
| |
| If the ordinal is positive, the returned value will be the _n_^th^ smallest value. |
| |
| If the ordinal is negative, the returned value will be the _n_^th^ largest value. |
| |
| `ordinal(<Constant Int>, < T >)` \=> `< _Single_ T >` |