With Repeat By, you can show multiple charts by groups at a time on the same chart area. It is useful to capture/compare the trends and characteristics of groups at a glance.
The Repeat By feature is available for following chart types.
Scatter (No Aggregation)
Scatter (With Aggregation)
You can assign a column you want to group by and repeat at the Repeat By control. Values in the assigned column are treated as discrete values (as text).
If you assign multiple columns to Y-Axis, you can treat those columns as groups and repeat the chart by those columns.
You can choose "(Each Y Axis)" option shows up in the Repeat By dropdown. This option shows up when you have assign multiple columns to Y-Axis.
The sorting order of the charts is ascending. If you assign a factor column to the Repeat By, it respects the order of factor levels.
You can open the Repeat By property dialog by clicking the gear icon at the Repeat By control.
Following options are available on the Repeat By property dialog.
Number of Columns
Static (1 - 15)
Fill All Charts in Viz Area
Sync Scales Among Charts
Take a look at following articles for more details about the Repeat By.