Salaried worker who worked in NY 4 days for my company and working days question

Yes, you must file Form IT-203, Nonresident and Part-Year Resident Income Tax Return, if you:

• were not a resident of New York State and received income during the tax year from New York State sources, or
• moved into or out of New York State during the tax year.

Your working days should not include weekends or vacation days if you did not work. 

If you are a New York State nonresident you must file Form IT-203, Nonresident and Part-Year Resident Income Tax Return, if you meet any of the following conditions:

• You are a nonresident with New York source income and your New York adjusted gross income Federal amount column (Form IT-203, line 31) exceeds your New York standard deduction.
• You want to claim a refund of any New York State, New York City, or Yonkers income taxes withheld from your pay.
• You want to claim any of the refundable or carryover credits available.
• You had a net operating loss for New York State personal income tax purposes for the tax year, without having a similar net operating loss for federal income tax purposes.