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--- transformations:aggregate [2020/02/10 11:21] – dmitry
+++ transformations:aggregate [2021/04/02 01:47] – craigt
@@ Line 1: / Line 1: @@
-===== Aggregate =====
+{{ transformations:AggregateAction.png}}
+====== AGGREGATE ======
+Category: Transform / Basic\\
-This transformation calculates the aggregates for selected columns grouped by another set of columns.
+\\
+=====Description=====
+This action calculates the aggregates for selected columns, grouped by another set of columns.
 Available aggregations:
@@ Line 11: / Line 15: @@
   * Max
   * Any
+  * Concatenate
-EXAMPLE
+\\
+=====Action settings=====
+^Setting^Description^
+|Calculate|Select the column in which the values will be aggregated.|
+|Aggregation method|Select the aggregation method to be used on the values in the chosen column.|
+|Group by|Select the column(s) in which the grouping of values will drive the aggregation.|
+You can aggregate more columns by the selected //Group by// columns by using the //Aggregate by more columns// option.
+The output of this action is a dataset containing the "Group by" column, plus an additional column for each aggregation chosen.\\
+\\
+=====Examples=====
+**Example 1:** Find out the longest river on each continent.
 **Source table:** The longest rivers in the world
-^  River  ^  Length(km)  ^  Continent  ^
+^ River  ^ Length(km)  ^ Continent  ^
-| Nile  |  6650  |  Africa  |
+| Nile  |  6650|Africa  |
-| Amazon  |  6400  |  South America  |
+| Amazon  |  6400|South America  |
-| Yangtze  |  6300  |  Asia  |
+| Yangtze  |  6300|Asia  |
-| Mississippi  |  6275  |  North America  |
+| Mississippi  |  6275|North America  |
-| Yenisei  |  5539  |  Asia  |
+| Yenisei  |  5539|Asia  |
-| Yellow River  |  5464  |  Asia  |
+| Yellow River  |  5464|Asia  |
-| Ob  |  5410  |  Asia  |
+| Ob  |  5410|Asia  |
-| Paraná  |  4880  |  South America  |
+| Paraná  |  4880|South America  |
-**Objective:** Find out the longest river on each continent.
+**Action parameters:**
-**Transformation parameters:**
+>Calculate: Length(km), Aggregation: Max
+>Group by: Continent
-  * Calculate: Length(km)
+**Output table:**
-  * Aggregation: Max
-  * Group by: Continent
+^Continent  ^Max of Length(km)  ^
+|Africa  |  6650|
+|Asia  |  6300|
+|North America  |  6275|
+|South America  |  6400|
+\\
+\\
+**Example 2:** Find out the longest river, and the number of rivers, on each continent.
+**Source table:** Same source table as Example 1.
+**Action parameters:**
+>Calculate: Length(km), Aggregation: Max
+>Calculate: River, Aggregation: Count
+>Group by: Continent
 **Output table:**
-^  River  ^  Continent  ^  Max of Length(km)  ^
+^Continent^Max of Length(km)^Count of River^
-| Nile  |  Africa  |  6650  |
+|Africa  |  6650|  1|
-| Yangtze  |  Asia  |  6300  |
+|Asia  |  6300|  3|
-| Mississippi  |  North America  |  6275  |
+|North America  |  6275|  1|
-| Amazon  |  South America  |  6400  |
+|South America  |  6400|  2|
+\\
+=====Shortcuts=====
+Fast ways to create the action:\\
+  *Right-click on a column heading, and select "Aggregate", then select the aggregation method from the submenu.
+  *Click the drop-down arrow in a column heading and select "Aggregate", then select the aggregation method.
-=== Notes ===
+\\
+=====See also=====
+  * [[transformations:addcolumn|Calculate new column(s)]]
+  * [[transformations:replacecolumn|Modify columns(s)]]
+  * [[transformations:Rule|Rule]]
-The "Any" aggregation picks only 1 arbitrary (random) value from a group of values and discards the rest.
-The "Any" aggregation is typically used for non-numeric values, where all values in a group are known to be the same. E.g. "Any" applied to "ABC", "ABC", "ABC" will return "ABC".