Filter actions are defined by source sheet(s) that pass one or more dimensional values as filters to Target sheets upon an action. Remember that every mark on a sheet is defined by a unique intersection of dimensional values. When an action occurs involving one or more of those marks, the dimensional values that comprise the mark(s) can be passed as filters to one or more Target sheets.

When you create or edit a filter action, you will see options similar to these:

This screen allows you to do the following:

• Name the filter.
• Choose Source and Target sheets. The Source sheet is where the user will initiate the action (hover, selection, menu) and the Target sheet is where the response will be applied (filtering in this example, but also highlighting).
• Set the action that triggers the filter and whether the selection of multiple marks or only a single mark initiates the action.
• Choose what happens when the selection is cleared.
• Specify which dimensions are used to pass filter values to the Target sheet(s).

You may select as many source and Target sheets as you desire. However, if you specify specific Target filters in the bottom section, the fields you select must be present in the Source sheet (for example, on Rows, Columns, and Detail). You will receive a warning if a field is not available for one or more Source sheets and the action will not be triggered for those sheets. Most of the time, your source and target will be the same dashboard. Optionally, you can specify a different Target sheet or dashboard, which will cause the action to navigate to the target in addition to filtering.

Filter actions can be set to occur on any one of three possible actions:

• Hover: The user moves the mouse cursor over a mark (or taps a mark on a mobile device).
• Select: The user clicks or taps a mark, and a rectangle/radial/lasso selects multiple marks by clicking and dragging a rectangle around them and clicks a header (in which case all marks for that header are selected). A user may deselect by clicking/tapping the already selected mark, clicking/tapping an empty space in the view, or by clicking/tapping the already selected header.
• Menu: The user selects the menu option for the action on the tooltip.

Consider the following example of a filter action that's triggered when a bar is selected in the source:

Each bar mark in the source is defined by the Category dimension. When the bar for Tables is selected, a single filter is set on the target.

If the mark is defined by more than one dimension (for example, Category and Region), then the Target sheet will still have a single filter with the combination of dimension values that had been selected. In this example, the filter contains Office Machines and West, matching the dimensions that define the selected square:

By default, all dimensions present in the source view are used in a filter action. Optionally, you can specify which fields should be used. You can use the Selected Fields option in the Edit Filter Actions dialogue to accomplish the following:

• Filter based on fewer dimensions. For example, if you only selected the Region field, then selecting the preceding square would only pass the West region as a filter to the target.
• Filter a target view using a different data source. The Selected Fields option allows you to map the source field to a target field (even if the target field has a different name, though the values must still match). For example, if the target used a data source where East was a possible value for a field named Area, you could map Region from the source to Area in the target.