Position a Datum Line
- From the Datum Lines panel, select a datum line from the datum list or from the screen.
 - Activate the Datum check box.
 - Click the Label tab.
 - 
                Enter a value in the Position field. The value can be any of the
                    following:
                
- A single value
 - A math expression that returns a single value (without curly brackets, {})
 - A math expression as a function of x or y, with x or y being the horizontal or vertical axes values, respectively.
 
 - 
                Select an Y or X axis
                    (optional).
                The datum line is moved to the new location on the plot.Note: The X or Y axis option does not apply to Polar Plots.
 - 
                Next to Location, select a button depicting a datum line label location in the
                    window.
                The datum line label is moved to the new position.