如何在chart.js中为条形图绘制基线答案

【问题标题】：How to draw baseline for bar chart in chart.js如何在chart.js中为条形图绘制基线
【发布时间】：2017-05-04 10:20:37
【问题描述】：

我有一个这样的条形图

我需要在下面画水平虚线

我正在使用图表 js 来创建这个图表。请帮我画出这条基线。

var ctx = document.getElementById("baseLinebar");

var myChart = new Chart(ctx, {
    type: 'bar',
    data: {
        labels: ["25", "60", "15", "30"],
        datasets: [{
            data: [25, 60, 15, 30],
            backgroundColor: [
                'rgba(255, 99, 132, 1)',
                'rgba(54, 162, 235, 1)',
                'rgba(255, 206, 86, 1)',
                'rgba(75, 192, 192, 1)'
            ]
        }]
    },
    options: {
        scales: {
            xAxes: [{
                        gridLines: {
                            display:false
                        },
                        barThickness:40
                    }],
            yAxes: [{
                        gridLines: {
                            display:false
                        }
                    }]

       }
    }
});

【问题讨论】：

标签： javascript jquery angularjs charts chart.js

【解决方案1】：

这里我们使用了horizonalLinePlugin 并将其注册到Chart pluginService。您可以在config 中使用horizontalLine 作为option 的属性。使用这个fiddle

var config = {
                type: 'bar',
                data: {
                    labels: ["25", "60", "15", "30"],
                    datasets: [{
                        data: [25, 60, 15, 30],
                        backgroundColor: [
                            'rgba(255, 99, 132, 1)',
                            'rgba(54, 162, 235, 1)',
                            'rgba(255, 206, 86, 1)',
                            'rgba(75, 192, 192, 1)'
                        ]
                    }]
                },
                options: {
                    scales: {
                        xAxes: [{
                            gridLines: {
                                display: true
                            },
                            barThickness: 40,
                            stacked: true

                        }],
                        yAxes: [{
                            gridLines: {
                                display: true
                            },
                            stacked: true

                        }]

                    },
                    horizontalLine: [{
                        y: 50,
                        style: "rgba(255, 0, 0, .4)",
                        text: "max"
                    },  {
                        y: 15,
                        text: "min"
                    }]
                }
            };

            ;
            var ctx = document.getElementById("canvas");

            var horizonalLinePlugin = {
                afterDraw: function (chartInstance) {
                    var yScale = chartInstance.scales["y-axis-0"];
                    var canvas = chartInstance.chart;
                    var ctx = canvas.ctx;
                    var index;
                    var line;
                    var style;

                    if (chartInstance.options.horizontalLine) {
                        for (index = 0; index < chartInstance.options.horizontalLine.length; index++) {
                            line = chartInstance.options.horizontalLine[index];

                            if (!line.style) {
                                style = "rgba(169,169,169, .6)";
                            } else {
                                style = line.style;
                            }

                            if (line.y) {
                                yValue = yScale.getPixelForValue(line.y);
                            } else {
                                yValue = 0;
                            }

                            ctx.lineWidth = 3;

                            if (yValue) {
                                ctx.beginPath();
                                ctx.moveTo(0, yValue);
                                ctx.lineTo(canvas.width, yValue);
                                ctx.strokeStyle = style;
                                ctx.stroke();
                            }

                            if (line.text) {
                                ctx.fillStyle = style;
                                ctx.fillText(line.text, 0, yValue + ctx.lineWidth);
                            }
                        }
                        return;
                    };
                }
            };
            Chart.pluginService.register(horizonalLinePlugin);

            var myChart = new Chart(ctx, config);

【讨论】：

【解决方案2】：

像这样试试。

Chart.js 确实有混合图表。

文档：http://www.chartjs.org/docs/#chart-configuration-mixed-chart-types

var ctx = document.getElementById("myChart").getContext('2d');
var myChart = new Chart(ctx, {
    type: 'bar',
    data: {
        labels: ['25', '60', '45'],
        datasets: [
          
            {
                type: 'line',
                label: 'Baseline',
                data: [15, 15, 15 ]
                
            },
            {
                type: 'bar',
                label: 'Marks',
                data: [25, 60, 45],
                 backgroundColor: [
                'rgba(255, 99, 132, 1)',
                'rgba(54, 162, 235, 1)',
                'rgba(255, 206, 86, 1)'
            ]
            }
            
        ]
    },
    options: {
    scales: {
        yAxes: [{
            ticks: {
                beginAtZero: true
            }
        }]
    }
}
});

.container {
  width: 80%;
  margin: 15px auto;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.2.2/Chart.min.js"></script>


<div class="container">
  <div>
    <canvas id="myChart"></canvas>
  </div>
</div>

【讨论】：