Convert data used for an ngGrid (Array of same-key objects) to something that will work for a google-chart focusing on the data attribute. It would be good to refactor this code to simply take an input array and convert to google-chart format. Call groupBy externally instead.

gistfile1.txt

var ngGridObj = [ {
	"entity" : {
		'date' : '2013-09-23 23:23:23',
		'amt' : 4.5,
		'name' : 'Mike'
	}
}, {
	"entity" : {
		'date' : '2013-09-26 23:23:23',
		'amt' : 6.5,
		'name' : 'Mike'
	}
}, {
	"entity" : {
		'date' : '2013-09-26 23:27:27',
		'amt' : 3,
		'name' : 'Maven'
	}
} ];
var ngGridX = 'date';
var ngGridY = 'amt';
var googleChartData = {
	"cols" : [ {
		"id" : "date",
		"label" : "date",
		"type" : "string"
	}, {
		"id" : "amt",
		"label" : "amt",
		"type" : "number"
	} ],
	"rows" : [ {
		"c" : [ {
			"v" : "2013-09-23 23:23:23"
		}, {
			"v" : 4.5
		} ]
	}, {
		"c" : [ {
			"v" : "2013-09-26 23:23:23"
		}, {
			"v" : 6.5
		} ]
	}, {
		"c" : [ {
			"v" : "2013-09-26 23:27:27"
		}, {
			"v" : 3,
		} ]
	}, ]
};
var googleChartData2 = {
	"cols" : [ {
		"id" : "date",
		"label" : "date",
		"type" : "string"
	}, {
		"id" : "amt",
		"label" : "amt",
		"type" : "number"
	} ],
	"rows" : [ {
		"c" : [ {
			"v" : "2013-09-23"
		}, {
			"v" : 4.5
		} ]
	}, {
		"c" : [ {
			"v" : "2013-09-24"
		}, {
			"v" : 0
		} ]
	}, {
		"c" : [ {
			"v" : "2013-09-25"
		}, {
			"v" : 0
		} ]
	}, {
		"c" : [ {
			"v" : "2013-09-26"
		}, {
			"v" : 9.5
		} ]
	}, ]
};
var googleChartData3 = {
	"cols" : [ {
		"id" : "date",
		"label" : "date",
		"type" : "string"
	}, {
		"id" : "amt",
		"label" : "amt",
		"type" : "number"
	} ],
	"rows" : [ {
		"c" : [ {
			"v" : "2013-09-01"
		}, {
			"v" : 4.666666666666667
		} ]
	}, ]
};
var googleChartData4 = {
	"cols" : [ {
		"id" : "name",
		"label" : "name",
		"type" : "string"
	}, {
		"id" : "amt",
		"label" : "amt",
		"type" : "number"
	} ],
	"rows" : [ {
		"c" : [ {
			"v" : "Mike"
		}, {
			"v" : 5.5
		} ]
	}, {
		"c" : [ {
			"v" : "Maven"
		}, {
			"v" : 3
		} ]
	}, ]
};

	it('should create a google chart obj given a ng-grid data source', function() {
		expect(ngGrid2GoogleChartData(ngGridObj, ngGridX, ngGridX, ngGridY, ngGridY, "none", "sum", "transactions > 2013-01-01").data).toEqual(googleChartData);
	});

	it('should create a google chart obj grouping by day and summing the group.  Missing days will fill in.', function() {
		expect(ngGrid2GoogleChartData(ngGridObj, ngGridX, ngGridX, ngGridY, ngGridY, "day", "sum", "transactions > 2013-01-01").data).toEqual(googleChartData2);
	});

	it('should create a google chart obj grouping by month and avg the group.  Missing months will fill in.', function() {
		expect(ngGrid2GoogleChartData(ngGridObj, ngGridX, ngGridX, ngGridY, ngGridY, "month", "avg", "transactions > 2013-01-01").data).toEqual(googleChartData3);
	});

	it('should create a google chart obj grouping by x value and avg the group.', function() {
		expect(ngGrid2GoogleChartData(ngGridObj, 'name', 'name', 'amt', 'amt', "x", "avg", "transactions > 2013-01-01").data).toEqual(googleChartData4);
	});

google-chart.html

<div google-chart chart="chart" style="{{chart.cssStyle}}"/>

ngGrid2GoogleChartData.js

/**
 * @method
 * @public
 * @description Convert data used for an ngGrid (Array of same-key objects) to
 *              something that will work for a google-chart focusing on the data
 *              attribute. It would be good to refactor this code to simply take
 *              an input array and convert to google-chart format. Call groupBy
 *              externally instead.
 * @param {array}
 *            gridRows - array of x/y values. Can include extra fields.
 * @param {string}
 *            xCol - name of x attribute.
 * @param {string}
 *            xLbl - Human readable version of xCol.
 * @param {string}
 *            yCol - name of y attribute.
 * @param {string}
 *            yLbl - Human readable version of yCol.
 * @param {string}
 *            chartGroup - day, month, x, none. Call grouping function if !none.
 * @param {string}
 *            chartAgg - max, sum, avg
 * @param {string}
 *            showing - used to build the title of the chart. (What data is
 *            showing?)
 * @return {object} chart - full google-chart data.
 */

function ngGrid2GoogleChartData(gridRows, xCol, xLbl, yCol, yLbl, chartGroup, chartAgg, showing) {

	var start = new Date();
	var MAX_ROWS = 500;
	var groupInput = [];
	var groupOutput = [];

	var chart = chartTemplate();
	var data = chart.data;
	data.cols = [];
	data.rows = [];
	var title = (chartGroup === "none") ? "" : chartAgg;
	title += " " + yLbl + " over " + xLbl + " for " + showing;
	chart.options.title = title;
	chart.options.vAxis.title = yLbl;
	chart.options.hAxis.title = xLbl;

	// No grouping: Push the ngGrid rows array into the google chart.
	if (chartGroup === "none") {
		for ( var idx = 0; idx < gridRows.length; idx++) {
			var gridRow = gridRows[idx];
			data.rows.push({
				"c" : [ {
					"v" : gridRow.entity[xCol]
				}, {
					"v" : gridRow.entity[yCol]
				}, ]
			});

			// Now that we are grouping, we need to count the output # of rows.
			if (data.rows.length >= MAX_ROWS) {
				break;
			}
		}
	} else {
		// Grouped! Push the grouped object into the google chart.

		groupInput = _.map(gridRows, function(row) {
			return row.entity;
		});
		groupOutput = groupBy(groupInput, xCol, yCol, chartGroup, chartAgg);

		_.each(groupOutput, function(row) {
			data.rows.push({
				"c" : [ {
					"v" : row[xCol]
				}, {
					"v" : row[yCol]
				}, ]
			});
		});
	}

	data.cols = [ {
		"id" : xCol,
		"label" : xCol,
		"type" : "string"
	}, {
		"id" : yCol,
		"label" : yCol,
		"type" : "number"
	}, ];

	var end = new Date();
	console.log("ngGrid2GoogleChartData processed " + gridRows.length + " rows in " + (end - start) + "ms.");

	return chart;
}

function chartTemplate() {
	var chartModel = {};
	chartModel = {
		"type" : "ColumnChart",
		"displayed" : true,
		"cssStyle" : "height:400px; width:100%;",
		"data" : {
			"cols" : [ {
				"id" : "date",
				"label" : "date",
				"type" : "string"
			}, {
				"id" : "amt",
				"label" : "amt",
				"type" : "number"
			} ],
			"rows" : [ {
				"c" : [ {
					"v" : "2013-09-25 23:23:23"
				}, {
					"v" : 4.5
				} ]
			}, {
				"c" : [ {
					"v" : "2013-09-26 23:23:23"
				}, {
					"v" : 6.5
				} ]
			}, {
				"c" : [ {
					"v" : "2013-09-27 23:23:23"
				}, {
					"v" : 3,
				} ]
			}, ]
		},
		"options" : {
			"title" : "Updating...",
			"isStacked" : "true",
			"fill" : 20,
			"displayExactValues" : true,
			"vAxis" : {
				"title" : ""
			},
			"hAxis" : {
				"title" : ""
			}
		},
		"formatters" : {}
	};
	return chartModel;
}