Stacked Column Chart (Using Flex Chart)

You can use this code on top of any Datamart, just adjust the last line of the code with the name of your:

Datamart Name
Dimension column name, used for X axis values.
Dimension column name, used for the series, which forms the stack.
Measure column name and operation, if you want to summarize the measure, or calculate the average, etc.

The result then looks like this:

Full code example which creates the Flex Chart

def stackedColumnChartDataFromDatamart(datamartTableName, dimensionColumnNameForX, dimensionColumnNameForStack, measureExpression) {
    def dmCtx = api.getDatamartContext()
    def salesDM = dmCtx.getDatamart(datamartTableName)
    def datamartQuery = dmCtx.newQuery(salesDM, true)
    datamartQuery.select(dimensionColumnNameForX, "dimX")
    datamartQuery.select(dimensionColumnNameForStack, "dimStacked")
    datamartQuery.select(measureExpression, "measure")
    datamartQuery.orderBy(dimensionColumnNameForX, dimensionColumnNameForStack)
    def result = dmCtx.executeQuery(datamartQuery)

    def rows = []
    for (def it = result.getData().iterator(); it.hasNext();) {
        def row = it.next()
        rows << [dimX: (row.dimX), dimStacked: (row.dimStacked), measure: (row.measure)]
    }

    return rows
}

def createStackedColumnChart(rows) {
    def serieNames = rows.collect { row -> row.dimStacked }.unique()
    def xValues = rows.collect { row -> row.dimX }.unique()

    //populate data array
    def values = [:]
    for (serieName in serieNames) for (xValue in xValues) values[serieName, xValue] = 0
    for (row in rows) values[row.dimStacked, row.dimX] = row.measure

    //create chart data series
    def series = []
    for (serieName in serieNames) {
        def data = xValues.collect { xValue -> [name: (xValue), y: (values[serieName, xValue])] }
        def serie = [name: (serieName), data: (data)]
        series << serie
    }

    //chart definition
    def chart = [
            chart      : [
                    type: 'column'
            ],
            xAxis      : [
                    categories: (xValues)
            ],
            plotOptions: [
                    column: [
                            stacking: 'normal'
                    ]
            ],
            series     : (series)
    ]


    return api.buildFlexChart(chart)
}

if (api.isInputGenerationExecution()) return

return createStackedColumnChart(
        stackedColumnChartDataFromDatamart("Sales_Data", "Invoice_DateYear", "ProductGroup", "SUM(Quantity)")
)