var rawData = [{
    "dimension": ["a", "c", "f"],
    "metric": [26]
}, {
    "dimension": ["a", "b", "e"],
    "metric": [12]
}, {
    "dimension": ["a", "d", "e"],
    "metric": [7]
}, {
    "dimension": ["a", "b", "f"],
    "metric": [5]
}, {
    "dimension": ["a", "c", "e"],
    "metric": [2]
}, {
    "dimension": ["a", "d", "f"],
    "metric": [1]
}, {
    "dimension": ["a", "k", ""],
    "metric": [2]
}];

output:
{
    name: 'start',
    children: [{
            name: 'a',
            children: [{
                    name: 'c',
                    children: [{
                        name: 'f',
                        value: 26
                    }, {
                        name: 'e',
                        value: 2
                    }]
                },
                {
                    name: 'b',
                    children: [{
                        name: 'e',
                        value: 12
                    }, {
                        name: 'f',
                        value: 5
                    }]
                },
                {
                    name: 'd',
                    children: [{
                        name: 'e',
                        value: 7
                    }, {
                        name: 'f',
                        value: 1
                    }]
                },
                {
                    name: 'k',
                    value: 2
                }
            ]
        },
        {
            name: 'b',
            children: [{
                name: 'c',
                children: [{
                    name: 'd',
                    value: 2
                }]
            }]
        }
    ]
}