A graduate student was the victim of an armed robbery in the East Rock neighborhood of the city at 10:32 p.m. Friday. According to an e-mail message sent to the Yale community by Yale Police Department Chief James Perrotti, the student was approached by two males, one of whom had a handgun, on Whitney Avenue near Cold Spring Street. The robbers took the woman’s purse, but she was not injured. No further information about the incident was available over the weekend.