Group by: documentation

Author: PrimozGodec

doc/visual-programming/source/widgets/data/groupby.md

@@ -0,0 +1,39 @@
+Group by
+========
+
+Groups data by selected variables and aggregate columns with selected aggregations.
+
+**Inputs**
+
+- Data: input data table
+
+**Outputs**
+
+- Data: aggregated data
+
+Group By widget first identifies groups based on selected variables in the **Group by** list. Groups are defined by all distinct combinations of values in selected variables.
+
+In the second step, the widget computes aggregations defined in the table on the right side of the widget for each group.
+
+
+![](images/Group-by-stamped.png)
+
+1. Select variables that define groups
+2. View variables and their aggregations. To change aggregation for one or more variables, select them in the table.
+3. Change aggregations for variables selected in the view above.
+4. When the *Send automatically* box is ticked, all changes will be automatically communicated to other widgets.
+5. Get documentation, observe a number of items on input or output
+
+Examples
+--------
+
+We first load **heart_disease** dataset in the **File** widget. In the **Group By** widget, we set variables that define groups -- **diameter narrowing** and **gender**. Each group includes items (rows) that belong to one combination of both variables. 
+
+In the table on the right-hand side of the widget, we set that we want to compute **mean** and  **median** for values of **rest SBP** variable in each group, **median** for values of **cholesterol** variable, and **mean** for **major vessels colored**.
+
+In the **Data Table** widget, we can see that both females and males have lower average values for **rest SBP** when **diameter narrowing** is 0. The difference is greater for females. The median of **rest SBP** is different only for females, while for males is the same.
+
+You can also observe differences between median **cholesterol** level and mean value of **major vessel colored** between groups.
+
+
+![](images/Group-by-Example.png)

doc/visual-programming/source/widgets/data/images/Group-by-example.png

@@ -311,6 +311,16 @@
     "background": "#FFD39F",
     "keywords": []
    },
+   {
+    "text": "Group by",
+    "doc": null,
+    "icon": "../Orange/widgets/data/icons/GroupBy.svg",
+    "background": "#FFD39F",
+    "keywords": [
+     "aggregate",
+     "group by"
+    ]
+   },
    {
     "text": "Melt",
     "doc": "visual-programming/source/widgets/data/melt.md",