user: Question: How many episodes were directed by Tim Matheson?
Columns: ['Series #', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (million)']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1.0, '"Pilot" "Welcome to the CIA"', 'Tim Matheson', 'Matt Corman & Chris Ord', 'July13,2010', 'CA101', '4.88']
SQL:

assistant: SELECT COUNT("Original air date") FROM "Table" WHERE "Directed by" = 'Tim Matheson';