问题
Since it seems impossible or highly difficult (no working answers here) to place a label above the last bar on a bar chart, I would like to now know how to place a label inside the last bar.
I am adding labels to all the bars of a horizontal bar chart with this code:
Chart.pluginService.register({
afterDraw: function (chartInstance) {
if (chartInstance.id !== 1) return; // affect this one only
var ctx = chartInstance.chart.ctx;
// render the value of the chart above the bar
ctx.font = Chart.helpers.fontString(14, 'bold', Chart.defaults.global.defaultFontFamily);
ctx.textAlign = 'center';
ctx.textBaseline = 'bottom';
chartInstance.data.datasets.forEach(function (dataset) {
for (var i = 0; i < dataset.data.length; i++) {
var model = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._model;
ctx.fillText(dataset.data[i] + (Number.isInteger(dataset.data[i]) ? ".0" : "") + "%", ((model.x + model.base) / 2), model.y + (model.height / 3));
}
});
}
});
That working chart looks like this:
...but this is a "regular" (vertical) bar chart, and my attempt to add a label to just the last bar like so:
Chart.pluginService.register({
afterDraw: function (chartInstance) {
if (chartInstance.id !== 2) return; // affect this one only
var ctx = chartInstance.chart.ctx;
// render the value of the chart above the bar
ctx.font = Chart.helpers.fontString(14, 'bold', Chart.defaults.global.defaultFontFamily);
ctx.textAlign = 'center';
ctx.textBaseline = 'center';
var model = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._model;
ctx.fillText(dataset.data[dataset.data.length - 1]);
}
});
...fails (nothing displays and, in fact, it causes problems not only with its own appearance, but that of other charts on the page, even though I use code to only apply this event to this particular chart:
So how can I calculate a value (based on last and penultimate bar values) and then place that calculated "label" inside the last bar in a Chart.JS bar chart?
With the code I attempted above, I just wanted to get the raw value for the bar inside the bar for now; the calculation portion of the logic can be left until later.
One possibility would be to make it a stacked bar chart, with nothing added to any of the bars but the last one, and then make its background color white to blend in with the chart background...
UPDATE
I tried my last idea; thinking maybe I could accomplish what I wanted by morphing my chart into a stacked bar chart (from a simple bar chart), adding a second set of mostly "zero" data as the second piece of the stack, like so:
Old code excerpt:
var forecastChartData = {
labels: [
"Total Sales"
],
datasets: [
{
label: "8/28/2016 - 9/3/2016",
backgroundColor: "rgba(255,0,0,0.75)",
hoverBackgroundColor: "rgba(255,0,0,1)",
data: [240]
},
{
label: "9/4/2016 - 9/10/2016",
backgroundColor: "rgba(255,153,0,0.75)",
hoverBackgroundColor: "rgba(255,153,0,1)",
data: [272]
},
{
label: "9/11/2016 - 9/17/2016",
backgroundColor: "rgba(255,255,0,0.75)",
hoverBackgroundColor: "rgba(255,255,0,1)",
data: [250]
},
{
label: "9/18/2016 - 9/24/2016",
backgroundColor: "rgba(0,255,0,0.75)",
hoverBackgroundColor: "rgba(0,255,0,1)",
data: [232]
},
{
label: "9/25/2016 - 10/1/2016",
backgroundColor: "rgba(0,0,255,0.75)",
hoverBackgroundColor: "rgba(0,0,255,1)",
data: [244]
}],
};
var forecastOptions = {
tooltips: {
enabled: true
}
};
New code:
var forecastChartData = {
labels: [
"Total Sales"
],
datasets: [
{
label: "8/28/2016 - 9/3/2016",
backgroundColor: "rgba(255,0,0,0.75)",
hoverBackgroundColor: "rgba(255,0,0,1)",
data: [240]
},
{
label: "9/4/2016 - 9/10/2016",
backgroundColor: "rgba(255,153,0,0.75)",
hoverBackgroundColor: "rgba(255,153,0,1)",
data: [272]
},
{
label: "9/11/2016 - 9/17/2016",
backgroundColor: "rgba(255,255,0,0.75)",
hoverBackgroundColor: "rgba(255,255,0,1)",
data: [250]
},
{
label: "9/18/2016 - 9/24/2016",
backgroundColor: "rgba(0,255,0,0.75)",
hoverBackgroundColor: "rgba(0,255,0,1)",
data: [232]
},
{
label: "9/25/2016 - 10/1/2016",
backgroundColor: "rgba(0,0,255,0.75)",
hoverBackgroundColor: "rgba(0,0,255,1)",
data: [244]
}],
[{
backgroundColor: "rgba(255, 255, 255, 0.5)",
hoverBackgroundColor: "rgba(200, 200, 200, 1)",
data: [0, 0, 0, 0, 5.2]
}]
};
var forecastOptions = {
scales: {
xAxes: [
{
stacked: true
}
],
yAxes: [
{
stacked: true
}
]
},
tooltips: {
enabled: true
}
};
But it didn't help at all; what am I doing wrong; if everything, how can I proceed after pursuing the nuclear option with my new code?
UPDATE 2
The code from Hung Tran here gets me close. My options is now:
var forecastOptions = {
tooltips: {
enabled: true
},
animation: {
duration: 500,
easing: "easeOutQuart",
onComplete: function () {
var ctx = this.chart.ctx;
ctx.font = Chart.helpers.fontString(Chart.defaults.global.defaultFontFamily, 'normal', Chart.defaults.global.defaultFontFamily);
ctx.textAlign = 'center';
ctx.textBaseline = 'bottom';
this.data.datasets.forEach(function (dataset) {
for (var i = 0; i < dataset.data.length; i++) {
var model = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._model,
scale_max = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._yScale.maxHeight;
ctx.fillStyle = '#444';
var y_pos = model.y - 5;
// Make sure data value does not get overflown and hidden
// when the bar's value is too close to max value of scale
// Note: The y value is reverse, it counts from top down
if ((scale_max - model.y) / scale_max >= 0.93)
y_pos = model.y + 20;
ctx.fillText(dataset.data[i], model.x, y_pos);
}
});
}
}
};
...and it places the data value above each bar.
As stated, this is close to what I want; what I really want, though, is the difference between the last value and the current value. For example, with this chart:
...what I want to see is:
240, 272 (30), 250 (-22), 232 (-18), 244 (12)
Or perhaps just a value above the last bar, either "244 (12)" or just "12".
That's what they say they want (the latter), but I wouldn't be surprised if they change their mind and want all the vals/diffs.
UPDATE 3
The solution adds no values atop the bars, and eats one of my slices of pie:
UPDATE 4
Here is pretty much all the code in Index.cshtml:
<style>
.pieLegend li span {
display: inline-block;
width: 12px;
height: 12px;
margin-right: 5px;
}
#piechartlegendleft {
height: 360px;
width: 100%;
}
#top10Legend {
display: inline-block;
}
#top10Legend > ul {
list-style: none;
}
#container {
display: inline-block;
height: 50%;
width: 50%;
}
</style>
<script>
$(document).ready(function () {
$("body").on("click", "#btnGetData",
. . .
});
Chart.defaults.global.defaultFontFamily = "Candara";
Chart.defaults.global.defaultFontSize = 16;
// Top 10 Pie Chart
var formatter = new Intl.NumberFormat("en-US");
Chart.pluginService.register({
afterDatasetsDraw: function (chartInstance) {
var ctx = chartInstance.chart.ctx;
ctx.font = Chart.helpers.fontString(14, 'bold', Chart.defaults.global.defaultFontFamily);
ctx.textAlign = 'center';
ctx.textBaseline = 'bottom';
ctx.fillStyle = '#666';
chartInstance.config.data.datasets.forEach(function (dataset) {
for (var i = 0; i < dataset.data.length; i++) {
var model = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._model,
total = dataset._meta[Object.keys(dataset._meta)[0]].total,
mid_radius = model.innerRadius + (model.outerRadius - model.innerRadius) / 2,
start_angle = model.startAngle,
end_angle = model.endAngle,
mid_angle = start_angle + (end_angle - start_angle) / 2;
var x = mid_radius * 1.5 * Math.cos(mid_angle);
var y = mid_radius * 1.5 * Math.sin(mid_angle);
ctx.fillStyle = '#fff';
if (i === 0 || i === 3 || i === 7 || i === 9) { // Darker text color for lighter background
ctx.fillStyle = '#000';
}
var percent = String(Math.round(dataset.data[i] / total * 100)) + "%";
// this prints the data number
// this prints the percentage
ctx.fillText(percent, model.x + x, model.y + y);
}
});
}
});
var data = {
labels: [
"Bananas (18%)",
"Lettuce, Romaine (14%)",
"Melons, Watermelon (10%)",
"Pineapple (10%)",
"Berries (10%)",
"Lettuce, Spring Mix (9%)",
"Broccoli (8%)",
"Melons, Honeydew (7%)",
"Grapes (7%)",
"Melons, Cantaloupe (7%)"
],
datasets: [
{
data: [2755, 2256, 1637, 1608, 1603, 1433, 1207, 1076, 1056, 1048],
backgroundColor: [
"#FFE135",
"#3B5323",
"#fc6c85",
"#ffec89",
"#021c3d",
"#3B5323",
"#046b00",
"#cef45a",
"#421C52",
"#FEA620"
]
}]
};
var optionsPie = {
responsive: true,
scaleBeginAtZero: true,
legend: {
display: false
},
tooltips: {
callbacks: {
label: function (tooltipItem, data) {
return data.labels[tooltipItem.index] + ": " +
formatter.format(data.datasets[tooltipItem.datasetIndex].data[tooltipItem.index]);
}
}
},
};
var ctx = $("#top10ItemsChart").get(0).getContext("2d");
var top10PieChart = new Chart(ctx,
{
type: 'pie',
data: data,
options: optionsPie
});
$("#top10Legend").html(top10PieChart.generateLegend());
// </ Top 10 Pie Chart
// Price Compliance Bar Chart
Chart.pluginService.register({
afterDraw: function (chartInstance) {
if (chartInstance.id !== 1) return; // affect this one only
var ctx = chartInstance.chart.ctx;
// render the value of the chart above the bar
ctx.font = Chart.helpers.fontString(14, 'bold', Chart.defaults.global.defaultFontFamily);
ctx.textAlign = 'center';
ctx.textBaseline = 'bottom';
ctx.fillStyle = "#000";
chartInstance.data.datasets.forEach(function (dataset) {
for (var i = 0; i < dataset.data.length; i++) {
var model = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._model;
ctx.fillText(dataset.data[i] + (Number.isInteger(dataset.data[i]) ? ".0" : "") + "%", ((model.x + model.base) / 2), model.y + (model.height / 3));
}
});
}
});
var ctxBarChart = $("#priceComplianceBarChart").get(0).getContext("2d");
var priceComplianceData = {
labels: [
"Bix Produce", "Capitol City", "Charlies Portland", "Costa Fruit and Produce",
"Get Fresh Sales", "Loffredo East", "Loffredo West", "Paragon", "Piazza Produce"
],
datasets: [
{
label: "Price Compliant",
backgroundColor: "rgba(34,139,34,0.5)",
hoverBackgroundColor: "rgba(34,139,34,1)",
data: [99.0, 99.2, 99.4, 98.9, 99.1, 99.5, 99.6, 99.2, 99.7]
},
{
label: "Non-Compliant",
backgroundColor: "rgba(255, 0, 0, 0.5)",
hoverBackgroundColor: "rgba(255, 0, 0, 1)",
data: [1.0, 0.8, 0.6, 1.1, 0.9, 0.5, 0.4, 0.8, 0.3]
}
]
}
var priceComplianceOptions = {
scales: {
xAxes: [
{
stacked: true
}],
yAxes: [
{
stacked: true
}]
},
tooltips: {
enabled: false
}
};
var priceBarChart = new Chart(ctxBarChart,
{
type: 'horizontalBar',
data: priceComplianceData,
options: priceComplianceOptions
});
// </Price Compliance Bar Chart
// Forecast/Impact Analysis chart
var ctxForecastChart = $("#forecastLineChart"); //.get(0).getContext("2d");
// See if the "olde style" makes any diff (used by the Chart.JS Whisperer)
//var ctxForecastChart = document.getElementById("forecastLineChart"); // no diff
var forecastChartData = {
labels: ["Total Sales"],
datasets: [
{
label: "8/28/2016 - 9/3/2016",
backgroundColor: "rgba(255,0,0,0.75)",
hoverBackgroundColor: "rgba(255,0,0,1)",
data: [240]
},
{
label: "9/4/2016 - 9/10/2016",
backgroundColor: "rgba(255,153,0,0.75)",
hoverBackgroundColor: "rgba(255,153,0,1)",
data: [272]
},
{
label: "9/11/2016 - 9/17/2016",
backgroundColor: "rgba(255,255,0,0.75)",
hoverBackgroundColor: "rgba(255,255,0,1)",
data: [250]
},
{
label: "9/18/2016 - 9/24/2016",
backgroundColor: "rgba(0,255,0,0.75)",
hoverBackgroundColor: "rgba(0,255,0,1)",
data: [232]
},
{
label: "9/25/2016 - 10/1/2016",
backgroundColor: "rgba(0,0,255,0.75)",
hoverBackgroundColor: "rgba(0,0,255,1)",
data: [244]
}]
};
var forecastOptions = {
tooltips: {
enabled: true
},
animation: {
duration: 500,
easing: "easeOutQuart",
onComplete: function () {
var ctx = this.chart.ctx;
ctx.font = Chart.helpers.fontString(Chart.defaults.global.defaultFontFamily, 'normal', Chart.defaults.global.defaultFontFamily);
ctx.textAlign = 'center';
ctx.textBaseline = 'bottom';
this.data.datasets.forEach(function (dataset) {
for (var i = 0; i < dataset.data.length; i++) {
var model = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._model,
scale_max = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._yScale.maxHeight;
ctx.fillStyle = '#444';
var y_pos = model.y - 5;
// Make sure data value does not get overflown and hidden
// when the bar's value is too close to max value of scale
// Note: The y value is reverse, it counts from top down
if ((scale_max - model.y) / scale_max >= 0.93)
y_pos = model.y + 20;
ctx.fillText(dataset.data[i], model.x, y_pos);
}
});
}
}
};
var forecastBarChart = new Chart(ctxForecastChart, {
type: 'bar',
//type: 'line',
data: forecastChartData,
options: forecastOptions
});
// </ Forecast/Impact Analysis chart
$('#delperfTable').DataTable({
"paging": false,
"info": false,
"searching": false
});
});
</script>
</head>
<body>
<div class="container body-content">
<div class="jumbotronjr">
<div class="col-md-3" style="margin-top: 0.6cm">
<img src="http://www.proactusa.com/wp-content/themes/proact/images/pa_logo_notag.png" height="86" width="133" alt="PRO*ACT usa logo">
</div>
<div class="col-md-9">
<label class="titletext" style="margin-top: 0.2cm;">Customer Dashboard</label>
<br />
<label class="titletextjr" style="margin-top: -2.2cm;" id="unitName">SODEXO</label>
<label class="cccsfont"> for the week of September 25 </label>
<input class="smalldatepicker" type="date" id="datepickerFrom" value="2016-09-25">
</input>
<label class="cccsfont"> to </label>
<input type="date" class="smalldatepicker" id="datepickerTo" value="2016-10-01">
</input>
<span id="newhourglass" class="fa fa-4x fa-refresh fa-spin boxRefresh hide" runat="server"></span>
<button class="btn btn-success btn-sm green" id="btnGetData"><span class="glyphicon glyphicon-refresh"></span></button>
</div>
</div>
<div class="row">
<div class="col-md-12">
<hr />
</div>
</div>
<div class="row">
<div class="col-md-12">
</div>
</div>
<div class="row" id="top10Items">
<div class="col-md-6">
<div class="topleft">
<h2 class="sectiontext">Top 10 Items</h2>
<br />
<div id="piechartlegendleft">
<div id="container">
<canvas id="top10ItemsChart" width="800" height="800"></canvas>
</div>
<div id="top10Legend" class="pieLegend"></div>
</div>
</div>
</div>
<div class="col-md-6">
<div class="topright">
<h2 class="sectiontext">Price Compliance</h2>
<div class="graph_container">
<canvas id="priceComplianceBarChart"></canvas>
</div>
</div>
</div>
</div>
<div class="row">
<div class="col-md-6">
<div class="bottomleft">
<h2 class="sectiontext">Forecast/Impact Analysis</h2>
<div class="graph_container">
<canvas id="forecastLineChart"></canvas>
</div>
</div>
</div>
<div class="col-md-6">
<div class="bottomright">
<h2 class="sectiontext">Delivery Performance</h2>
<table id="delperfTable">
. . .
</table>
</div>
</div>
</div>
</div>
</body>
</html>
回答1:
In your animation.onComplete callback, you can get the previous dataset with the following code :
// `dataset` here -----------------------------------------┐
// is the current dataset you are working on |
// (since you loop through all of them in your callback) V
var previousDataset = chartInstance.config.data.datasets[dataset._meta[Object.keys(dataset._meta)[0]].controller.index - 1];
Now that you can access the previous dataset, you can also get its value. Follows the full callback to make it more understandable :
var forecastOptions = {
tooltips: {
enabled: true
},
animation: {
duration: 500,
easing: "easeOutQuart",
onComplete: function() {
var ctx = this.chart.ctx;
ctx.font = Chart.helpers.fontString(Chart.defaults.global.defaultFontFamily, 'normal', Chart.defaults.global.defaultFontFamily);
ctx.textAlign = 'center';
ctx.textBaseline = 'bottom';
this.data.datasets.forEach(function(dataset) {
for (var i = 0; i < dataset.data.length; i++) {
// We get the previous dataset here
var previousDataset = dataset._meta[Object.keys(dataset._meta)[0]].controller.chart.config.data.datasets[dataset._meta[Object.keys(dataset._meta)[0]].controller.index - 1];
var model = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._model;
var scale_max = dataset._meta[Object.keys(dataset._meta)[0]].data[i]._yScale.maxHeight;
ctx.fillStyle = '#444';
var y_pos = model.y - 5;
if ((scale_max - model.y) / scale_max >= 0.93)
y_pos = model.y + 20;
// If the previous dataset is not `undefined` (actually exists) ..
if(typeof previousDataset !== "undefined") {
// We write the data, with the difference with the previous one
ctx.fillText(dataset.data[i] + " (" + (dataset.data[i] - previousDataset.data[i]) + ")", model.x, y_pos);
}
else {
// We only write the data
ctx.fillText(dataset.data[i], model.x, y_pos);
}
}
});
}
}
};
You can see this callback working on this jsFiddle, and here is its result :
Note: Feel free to comment if you need any small changes such as a percentage difference instead.
来源：https://stackoverflow.com/questions/39779510/how-can-i-calculate-a-value-and-place-it-inside-the-last-bar-in-a-chart-js-bar-c