I am trying to figure out how to add a trendline to my google line chart but am failing miserably. Is anyone able to point me in the right direction? I have seen that google do not provide a way to do this on a line chart but have also seen that it is possible to add a new series into the chart to achieve something similar. Here is what I have so far which works great besides not having a trendline. I have tried a few suggestions I found online but none of them made the maths clear to get the trendline to be a straight line:

function drawChartCustomerRevenue_93() {

    var revenueChart_93;

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

    data.addColumn('string', Date);

    data.addColumn('number', 'Sales Value');

    data.addRow(['Apr 2013', 271176.940000000]);

    data.addRow(['May 2013', 419031.540000000]);

    data.addRow(['Jun 2013', 429155.540000000]);

    data.addRow(['Jul 2013', 443780.400000000]);

    data.addRow(['Aug 2013', 320353.540000000]);

    data.addRow(['Sep 2013', 310640.910000000]);

    data.addRow(['Oct 2013', 252187.700000000]);

    data.addRow(['Nov 2013', 301414.560000000]);

    data.addRow(['Dec 2013', 224296.850000000]);

    data.addRow(['Jan 2014', 291131.140000000]);

    data.addRow(['Feb 2014', 354750.680000000]);

    data.addRow(['Mar 2014', 312736.710000000]);

    var formatter = new google.visualization.NumberFormat({

        fractionDigits: 2,

        prefix: '£'

    });

    formatter.format(data, 1);

    var chartHeight = 400;

    var chartWidth = 500;

    var chartOptions = {

        trendlines: {

            {

                color: 'green',

            }

        },

        title: '1: TEST NAME',

        isStacked: true,

        width: chartWidth,

        height: chartHeight,

        colors: ['#0000D4'],

        hAxis: {

            title: 'Sales Value (£)',

            slantedText: true,

            slantedTextAngle: 45,

            textStyle: {

                fontSize: 10

            },

        },

        chartArea: {

            left: 100,

            top: 20,

            width: (chartWidth - 10),

            height: (chartHeight - 90)

        }

    };

    revenueChart_93 = new google.visualization.LineChart(document.getElementById('CustomerRevenue_93'));

    revenueChart_93.draw(data, chartOptions);

};

drawChartCustomerRevenue_93();

EDIT:

I have now attempted to put the code in suggested to me but it still shows no trendline:

function drawChartCustomerRevenue_93() {

    var revenueChart_93;

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

    data.addColumn('date', 'Date');

    data.addColumn('number', 'Sales Value');

    data.addRow([new Date(2013, 4, 1), 184656.440000000]);

    data.addRow([new Date(2013, 5, 1), 420286.250000000]);

    data.addRow([new Date(2013, 6, 1), 431562.840000000]);

    data.addRow([new Date(2013, 7, 1), 446187.800000000]);

    data.addRow([new Date(2013, 8, 1), 320353.540000000]);

    data.addRow([new Date(2013, 9, 1), 313364.960000000]);

    data.addRow([new Date(2013, 10, 1), 252187.700000000]);

    data.addRow([new Date(2013, 11, 1), 303874.560000000]);

    data.addRow([new Date(2013, 12, 1), 224296.850000000]);

    data.addRow([new Date(2014, 1, 1), 297499.970000000]);

    data.addRow([new Date(2014, 2, 1), 354950.680000000]);

    data.addRow([new Date(2014, 3, 1), 315529.610000000]);

    data.addRow([new Date(2014, 4, 1), 145219.710000000]);

    var formatter = new google.visualization.NumberFormat({

        fractionDigits: 2,

        prefix: '£'

    });

    formatter.format(data, 1);

    var dateFormatter = new google.visualization.NumberFormat({

        pattern: 'MMM yyyy'

    });

    dateFormatter.format(data, 0);

    var chartHeight = 320;

    var chartWidth = 400;

    var chartOptions = {

        trendlines: {

            0: {

                color: 'green'

            }

        },

        title: '1: Test Name',

        isStacked: true,

        width: chartWidth,

        height: chartHeight,

        colors: ['#0000D4'],

        hAxis: {

            title: 'Sales Value (£)',

            slantedText: true,

            slantedTextAngle: 45,

            textStyle: {

                fontSize: 10

            },

            format: 'MMM yyyy',

        },

        chartArea: {

            left: 100,

            top: 20,

            width: (chartWidth - 8),

            height: (chartHeight - 72)

        }

    };

    revenueChart_93 = new google.visualization.LineChart(document.getElementById('CustomerRevenue_93'));

    revenueChart_93.draw(data, chartOptions);

};

drawChartCustomerRevenue_93();