Expression rules allow you to apply a single expression to a computation used in a chart. Points that violate the Expression rule will have their color changed to either the Highlight Color or Last Point Highlight Color, regardless of where they fall on the chart.
For example, if you visualize a measure with values that range from 0 to 100 against a time period of 365 days, you can define an Expression rule to highlight days where the measure was above 50.
Configuring an Expression rule
Name
A display name for the threshold.
The default value is "My Expression rule".
Drill Fields
If your chart uses drill fields, you can use this option to specify at which level of the drill view to apply the rule. For example, if your Drill Field contains Year, Quarter, and Month levels, and you specify Month as your threshold rule's Drill Field, you will only see the application of the rule when you drill into the Month level on your chart.
Expression
The expression contains the rule that is evaluated at each point in your graph. You can create it by entering the expression directly in the Expression field. Alternatively, click f(x) to use the Expression Editor to build the expression.
Computation
Use Computation to specify the data point that should be highlighted when the rule is satisfied.
Highlight all columns
If you are applying a single point threshold to a table, a cell in the row that contains a data point that violates the threshold is highlighted. You can also choose whether to highlight the cells in some or all of the other columns for the corresponding row. To highlight all columns in the row, make sure Highlight all columns is selected.
The default value is False.
Additional Columns to Highlight
If Highlight all columns is set to False, you can select which columns to highlight. Click the arrow to display a drop down list of available columns. Click a column name to select it. To remove a column from highlighting, click the 'x' next to its name.