var options = {
    id: "chart",
    axis: {
        x: {
            tick: {
                rotate: -60
            }
        }
    },
    data: {
        file: {
            url: '../../data/data_user.json',
            type: 'json'
        },
        keys: {
            name: 'user',
            value: 'access_count'
        }
    }
};
var barChart = new C9.BarChart(options);
barChart.draw();

[{
  "user": "Christine",
  "access_count": 54
}, {
  "user": "Christopher",
  "access_count": 53
}, {
  "user": "Ryan",
  "access_count": 76
}, {
  "user": "George",
  "access_count": 76
}, {
  "user": "Mary",
  "access_count": 24
}, {
  "user": "Carol",
  "access_count": 27
}, {
  "user": "Melissa",
  "access_count": 28
}, {
  "user": "Todd",
  "access_count": 84
}, {
  "user": "Terry",
  "access_count": 11
}, {
  "user": "Beverly",
  "access_count": 38
}, {
  "user": "Roy",
  "access_count": 94
}, {
  "user": "Brenda",
  "access_count": 26
}, {
  "user": "Frank",
  "access_count": 5
}, {
  "user": "Eugene",
  "access_count": 54
}, {
  "user": "Joseph",
  "access_count": 7
}]