Creating pivoted DataView from existing google cha

Question

I have a DataTable that contains:

id,day,proj,col1,col2,subtype,time
1,Nov 28,projectA,1050,880,foo,17481
2,Nov 28,projectA,1050,880,bar,16098
3,Nov 28,projectA,1080,40,foo,13509
4,Nov 28,projectA,1080,40,bar,9031

But would like to create a new pivoted DataView containing:

id,day,proj,col1,col2,foo,bar
1,Nov 28,projectA,1050,880,17481,16098
3,Nov 28,projectA,1080,40,13509,9031

Which I'd then like to create a stacked columnChart for.

There's a pivot clause in the query language, but how do I pivot data that's already in a DataTable?

Answer 1

Manually.

You can see this example on jsfiddle by asgallant. This uses a dataView to accomplish the task.

google.load('visualization', '1', {packages: ['table']});
google.setOnLoadCallback(drawChart);

function drawChart() {
    var data = new google.visualization.DataTable();
    data.addColumn('number', 'A');
    data.addColumn('string', 'B');
    data.addColumn('number', 'C');
    data.addRows([
        [1, 'foo', 6],
        [2, 'foo', 2],
        [3, 'foo', 1],
        [4, 'foo', 3],
        [1, 'bar', 7],
        [2, 'bar', 3],
        [1, 'baz', 8],
        [2, 'baz', 4]
    ]);

    var table1 = new google.visualization.Table(document.getElementById('table1'));
    table1.draw(data, {});

    /* manually pivot the data table
     * set column A as the first column in the view, 
     * then we have to separate out the C values into their own columns
     * according to the value of B, using a DataView with calculated columns
     */
    var view = new google.visualization.DataView(data);
    view.setColumns([0, {
        type: 'number',
        label: 'foo',
        calc: function (dt, row) {
            // return values of C only for the rows where B = "foo"
            return (dt.getValue(row, 1) == 'foo') ? dt.getValue(row, 2) : null;
        }
    }, {
        type: 'number',
        label: 'bar',
        calc: function (dt, row) {
            // return values of C only for the rows where B = "bar"
            return (dt.getValue(row, 1) == 'bar') ? dt.getValue(row, 2) : null;
        }
    }, {
        type: 'number',
        label: 'baz',
        calc: function (dt, row) {
            // return values of C only for the rows where B = "baz"
            return (dt.getValue(row, 1) == 'baz') ? dt.getValue(row, 2) : null;
        }
    }]);

    // next, we group the view on column A, which gets us the pivoted data
    var pivotedData = google.visualization.data.group(view, [0], [{
        column: 1,
        type: 'number',
        label: view.getColumnLabel(1),
        aggregation: google.visualization.data.sum
    }, {
        column: 2,
        type: 'number',
        label: view.getColumnLabel(2),
        aggregation: google.visualization.data.sum
    }, {
        column: 3,
        type: 'number',
        label: view.getColumnLabel(3),
        aggregation: google.visualization.data.sum
    }]);

    var table2 = new google.visualization.Table(document.getElementById('table2'));
    table2.draw(pivotedData, {});
}

Alternatively, you can do it the manual way.

      var data = new google.visualization.DataTable();

      data.addColumn('string', 'First Column Title');

      var baseline = chartData.getValue(chartData.getNumberOfRows() - 1, 15);

      for (var i = 0; i < chartData.getNumberOfRows(); i++) {
        data.addColumn('number', chartData.getFormattedValue(i, 0));
      };

      for (var j = 0; j < chartData.getNumberOfColumns() - 2; j++) {
        data.addRow();
        data.setValue(j, 0, chartData.getColumnLabel(j + 1));
        for (var i = 0; i < chartData.getNumberOfRows(); i++) {
          data.setValue(j, i + 1, chartData.getValue(i, j+1));
        };
      };