概述
本 Demo 展示了如何为图表添加趋势线并进行自定义配置。Demo 包含两个工作表：
Basic 工作表：演示线性趋势线和指数趋势线的基本用法
Advance 工作表：演示多项式趋势线的高级配置（显示公式和 R² 值）以及趋势线的前向预测功能
实现思路
准备两份数据源：广告投放与销售数据、月度销售数据
创建四个图表：两个散点图和两个柱状图
为每个图表的数据系列添加不同类型的趋势线
配置趋势线的样式、阶数、公式显示和预测周期等属性
代码解析
添加线性趋势线
这段代码创建了一个散点图，并为其第一个系列添加线性趋势线。通过 series().get() 获取系列对象，设置 trendlines 属性后，再用 series().set() 更新。趋势线的颜色设置为红色，宽度为 2。
配置多项式趋势线并显示公式
这段代码配置了一个 4 阶多项式趋势线。order 属性设置多项式的阶数（2-6），displayEquation 和 displayRSquared 属性分别控制是否在图表上显示趋势线公式和 R² 值。
设置趋势线前向预测
这段代码添加指数趋势线，并通过 forward: 3 将趋势线向前延伸 3 个周期进行预测。同时使用虚线样式（dashStyle: GC.Spread.Sheets.Charts.LineDashStyle.dash）区分趋势线和数据线。
运行效果
Basic 工作表：
第一个散点图显示广告投放与销量的关系，包含红色线性趋势线
第二个柱状图显示月度销售数据，包含橙色虚线的指数趋势线
Advance 工作表：
第一个散点图显示带公式和 R² 值的 4 阶多项式趋势线
第二个柱状图显示向前预测 3 个周期的指数趋势线
API 参考
趋势线配置属性
type：趋势线类型，使用 GC.Spread.Sheets.Charts.TrendlineType 枚举（linear、exponential、polynomial 等）
order：多项式趋势线的阶数（2-6）
forward / backward：向前或向后预测的周期数
displayEquation：是否显示趋势线公式
displayRSquared：是否显示 R² 值
style：趋势线样式，包括 color、width、dashStyle 等
period：移动平均趋势线的周期数
系列操作方法
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);
}
<!doctype html>
<html style="height:100%;font-size:14px;">
<head>
<meta name="spreadjs culture" content="zh-cn" />
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<link rel="stylesheet" type="text/css"
href="$DEMOROOT$/zh/purejs/node_modules/@grapecity-software/spread-sheets/styles/gc.spread.sheets.excel2013white.css">
<script src="$DEMOROOT$/zh/purejs/node_modules/@grapecity-software/spread-sheets/dist/gc.spread.sheets.all.min.js"
type="text/javascript"></script>
<script
src="$DEMOROOT$/zh/purejs/node_modules/@grapecity-software/spread-sheets-shapes/dist/gc.spread.sheets.shapes.min.js"
type="text/javascript"></script>
<script
src="$DEMOROOT$/zh/purejs/node_modules/@grapecity-software/spread-sheets-charts/dist/gc.spread.sheets.charts.min.js"
type="text/javascript"></script>
<script src="$DEMOROOT$/spread/source/js/license.js" type="text/javascript"></script>
<script src="app.js" type="text/javascript"></script>
<link rel="stylesheet" type="text/css" href="styles.css">
</head>
<body>
<div class="sample-tutorial">
<div class="sample-tutorial">
<div id="ss" class="sample-spreadsheets"></div>
</div>
</div>
</body>
</html>
.sample-tutorial {
position: relative;
height: 100%;
overflow: hidden;
}
.sample-spreadsheets {
width: 100% ;
height: 100%;
overflow: hidden;
float: left;
}
body {
position: absolute;
top: 0;
bottom: 0;
left: 0;
right: 0;
}
