PercentOfTotal
The PercentOfTotal function returns the percent of total for an aggregate formula.
This function is shorthand for: aggregate / Subtotal(aggregate, mode, parameters).
Syntax
PercentOfTotal(aggregate, [mode], [parameters])
Function arguments:
 aggregate (required)  The aggregate formula to use

mode (optional)  The mode to use when calculating the aggregate formula. Mode determines which dimension(s) to use when performing the calculation.
 General purpose modes

“grand_total”
(default for visualizations and pivot tables)  Calculates the percent of grand total for the aggregate formula.

 Visualization modes

“color”
 Calculates the aggregate percent of total using only the column specified for COLOR. 
“x_axis”
 Calculates the aggregate percent of total using only the column(s) placed on the XAXIS. 
“trellis_column”
/“trellis_row”
Calculates the aggregate percent of total using only the dimension specified for the TRELLIS COLUMN or TRELLIS ROW.

 Pivot table modes

“column”
/“row”
 Calculates aggregate percent of total for the column or row total. 
“column_parent”
/“row_parent”
 Calculates the aggregate percent of total for the column or row total, relative to the subtotal calculation for the parent dimensions.

 Table modes

“grouping_parent”
(default for tables)  Calculates the aggregate formula using the grouping keys from a parent grouping. This is equivalent to creating the aggregate calculation in a parent grouping and referencing it from a column in a lower grouping.

 General purpose modes

parameters (optional)  An additional parameter specific to the mode.
 Only applicable to the following modes: "column_parent", "row_parent" and "grouping_parent". For these modes, this 3rd parameter specifies how many parent dimensions to ignore.
Examples
PercentOfTotal(Sum([Quantity] * [Price]), "row")
 The numerator of the percentage is the aggregate formula calculated along rows and columns.
 The denominator of the percentage is the aggregate formula calculated along the rows.
 The pivot table subtotals calculate the percent of total at the expected granularity.
PercentOfTotal(Sum([Quantity] * [Price]), "x_axis")
 The numerator of the percentage is the aggregate formula calculated along the xaxis and color.
 The denominator of the percentage is the aggregate formula calculated along the xaxis.
 The calculation is shown in the tooltip, but is usable anywhere an aggregate formula is allowed.