趋势线是用来表示数据列中的斜率（或趋势）的附加线，又称为最佳拟合线。
因为趋势线可以根据当前数据预测未来值，所以在分析数据时可能会有所帮助。
用户可以为其图表创建6种不同类型的趋势线：包括线性，指数，对数，多项式，幂和移动平均值。
Linear: 最佳拟合直线。
Exponential: 用指数曲线说明数据值增大或减小然后稳定。
Logarithmic: 用对数曲线说明数据值快速增大或减小然后稳定。
Polynomial: 基于多项式的波动曲线。
Power: 以特定速率增加的曲线。
MovingAverage: 移动平均值曲线。
趋势线支持如下的图表类型：
Column
Bar
Line
Scatter
Area
你可以通过如下示例代码添加一条线性趋势线。
自定制
order: 在多项式趋势线中指定项数，取2到6之间的整数。
intercept: 指定“线性”，“指数”，“多项式”趋势线的截距。
displayEquation & displayRSquared: 指定是否显示趋势线的公式和R方。
forward & backward: 向前或向后预测数据。
（displayEquation，displayRSquared，forward，backward属性支持“线性”，“多项式”，“指数”，“对数”，“幂” 趋势线。）
style: 指定趋势线的样式，包括颜色，宽度和线型。
name: 指定趋势线的名称。 如果未指定名称，则将使用内置名称。
Period: 指定MovingAverage的周期，即是2到数据计数减1之间的整数。
var advData = [
['Advertising', 'Items sold'],
[28, 17],
[34, 19],
[41, 18],
[47, 20],
[52, 24],
[59, 26],
[65, 29],
[72, 31],
[80, 34],
[87, 39],
[94, 40],
[102, 42],
];
var salesData = [
['', 'Sales'],
['Jan', 54],
['Feb', 60],
['Mar', 86],
['Apr', 92],
['May', 112],
['Jun', 157],
['Jul', 202],
['Aug', 195],
['Sep', 187],
['Oct', 194],
['Nov', 238],
['Dec', 289],
];
window.onload = function () {
var spread = new GC.Spread.Sheets.Workbook(document.getElementById("ss"), { sheetCount: 2 });
initSheet1(spread);
initSheet2(spread);
};
function initSheet1(spread) {
var sheet1 = spread.getSheet(0);
sheet1.name('Basic');
sheet1.setArray(0, 0, advData);
sheet1.setArray(18, 0, salesData);
for (var i = 0; i < 12; i ++) {
sheet1.getCell(i + 1, 0).formatter('$#,##0');
}
// Choose a suitable trendline type from GC.Spread.Sheets.Charts.TrendlineType to fit your chart
var chart1 = sheet1.charts.add("chart1", GC.Spread.Sheets.Charts.ChartType.xyScatter, 130, 5, 500, 350, "A1:B13", GC.Spread.Sheets.Charts.RowCol.columns);
var axes = chart1.axes();
axes.primaryValue.title.text = 'Items sold';
axes.primaryCategory.title.text = 'Advertising';
axes.primaryCategory.majorGridLine.visible = true;
axes.primaryCategory.majorUnit = 10;
chart1.axes(axes);
var targetSeriesIndex = 0;
var targetSeries = chart1.series().get(targetSeriesIndex);
var linearTrendline = {
type: GC.Spread.Sheets.Charts.TrendlineType.linear,
style: {
color: 'red',
width: 2
}
};
targetSeries.trendlines = [ linearTrendline ];
chart1.series().set(targetSeriesIndex, targetSeries);
var chart2 = sheet1.charts.add("chart2", GC.Spread.Sheets.Charts.ChartType.columnClustered, 130, 360, 500, 350, "A19:B31", GC.Spread.Sheets.Charts.RowCol.columns);
var targetSeriesIndex = 0;
var targetSeries = chart2.series().get(targetSeriesIndex);
var exponentialTrendline = {
type: GC.Spread.Sheets.Charts.TrendlineType.exponential,
style: {
color: 'orange',
width: 2,
dashStyle: GC.Spread.Sheets.Charts.LineDashStyle.dash
}
};
targetSeries.trendlines = [ exponentialTrendline ];
chart2.series().set(targetSeriesIndex, targetSeries);
}
function initSheet2(spread) {
// More settings
var sheet2 = spread.getSheet(1);
sheet2.name('Advance');
sheet2.setArray(0, 0, advData);
sheet2.setArray(18, 0, salesData);
for (var i = 0; i < 12; i ++) {
sheet2.getCell(i + 1, 0).formatter('$#,##0');
}
// Change the order(the highest power for the independent variable) of polynomial trendline to adjust R-squared value
// Also you could show the equation and R-squared value in chart area if you want
var chart3 = sheet2.charts.add("chart3", GC.Spread.Sheets.Charts.ChartType.xyScatter, 130, 5, 500, 350, "A1:B13", GC.Spread.Sheets.Charts.RowCol.columns);
var axes = chart3.axes();
axes.primaryValue.title.text = 'Items sold';
axes.primaryCategory.title.text = 'Advertising';
axes.primaryCategory.majorGridLine.visible = true;
axes.primaryCategory.majorUnit = 10;
chart3.axes(axes);
var targetSeriesIndex = 0;
var targetSeries = chart3.series().get(targetSeriesIndex);
var polynomialTrendline = {
type: GC.Spread.Sheets.Charts.TrendlineType.polynomial,
order: 4,
displayEquation: true,
displayRSquared: true,
style: {
color: 'red',
width: 2
}
};
targetSeries.trendlines = [ polynomialTrendline ];
chart3.series().set(targetSeriesIndex, targetSeries);
// Set a value in the Forward and Backward fields to project your data into the future.
var chart4 = sheet2.charts.add("chart4", GC.Spread.Sheets.Charts.ChartType.columnClustered, 130, 360, 500, 350, "A19:B31", GC.Spread.Sheets.Charts.RowCol.columns);
var targetSeriesIndex = 0;
var targetSeries = chart4.series().get(targetSeriesIndex);
var exponentialTrendline = {
type: GC.Spread.Sheets.Charts.TrendlineType.exponential,
forward: 3,
style: {
color: 'orange',
width: 2,
dashStyle: GC.Spread.Sheets.Charts.LineDashStyle.dash
}
};
targetSeries.trendlines = [ exponentialTrendline ];
chart4.series().set(targetSeriesIndex, targetSeries);
}
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