a factor with levels Alabama
Alaska, Arizona, Arkansas California,
Colorado, Connecticut, Delaware, District of
Columbia, Florida,Georgia, Hawaii, Idaho,
Illinois, Indiana, Iowa Kansas Kentucky,
Louisiana, Maine, Maryland, Massachusetts,
Michigan, Minnesota, Mississippi, Missour,
Montana Nebraska, Nevada, New Hampshire, New
Jersey, New Mexico, New York, North Carolina, North
Dakota, Ohio, Oklahoma, Oregon, Pennsylvania,
Rhode Island, South Carolina, South Dakota,
Tennessee, Texas, Utah, Vermont, Virginia
Washington, West Virginia, Wisconsin, and Wyoming