How do I determine what filegroup my partition data is stored in?

This turned out to be tougher than I thought it would. I had to do some serious BOL research to figure out the connection (sys.allocation_units). I decided to include the approximate number of rows from sys.partitions as some extra information.

DECLARE @TableName sysname = 'MyTable';

SELECT p.partition_number, fg.name, p.rows
FROM sys.partitions p
    INNER JOIN sys.allocation_units au
    ON au.container_id = p.hobt_id
    INNER JOIN sys.filegroups fg
    ON fg.data_space_id = au.data_space_id
WHERE p.object_id = OBJECT_ID(@TableName)