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I had applied some gradient rule to my chartjs chart. And it looks great as you can see on the below
However, when the browser window is resized (i.e. width of window is smaller), the gradient is ruined (bottom blue colors disappeared). Screenshot:
I want to maintain the graph's gradient with all values and fit the different widths (responsive). Is there any way to do that? Here is what I had tried but didn't work:
.TS File
ngAfterViewInit() {
const ctx = (<HTMLCanvasElement>this.myChart.nativeElement).getContext('2d');
const purple_orange_gradient = ctx.createLinearGradient(0, 200, 0, 20);
purple_orange_gradient.addColorStop(0.1, "#000279");
purple_orange_gradient.addColorStop(0.2, "#0000F2");
purple_orange_gradient.addColorStop(0.3, "#0362FD");
purple_orange_gradient.addColorStop(0.4, "#04D3FD");
purple_orange_gradient.addColorStop(0.5, "#45FFB7");
purple_orange_gradient.addColorStop(0.6, "#B7FF46");
purple_orange_gradient.addColorStop(0.7, "#FFD401");
purple_orange_gradient.addColorStop(0.8, "#FE6500");
purple_orange_gradient.addColorStop(0.9, "#F30004");
purple_orange_gradient.addColorStop(1, "#7E0100");
const bar_chart = new Chart(ctx, {
type: "horizontalBar",
data: {
labels: []=this.histogramLabels.reverse(),
datasets: [{
borderColor: purple_orange_gradient,
pointBorderColor: purple_orange_gradient,
pointBackgroundColor: purple_orange_gradient,
pointHoverBackgroundColor: purple_orange_gradient,
pointHoverBorderColor: purple_orange_gradient,
pointBorderWidth: 10,
pointHoverRadius: 10,
pointHoverBorderWidth: 1,
pointRadius: 3,
fill: true,
backgroundColor: purple_orange_gradient,
borderWidth: 4,
data: []=this.histogramGraphData
}]
},
options: {
legend: {
display:false,
position: "bottom"
},
scales: {
yAxes: [{
ticks: {
display: false,
fontColor: "rgba(0,0,0,0.5)",
fontStyle: "bold",
beginAtZero: true,
maxTicksLimit: 1,
padding: 20,
},
gridLines: {
drawTicks: false,
display: false
}
}],
xAxes: [{
gridLines: {
zeroLineColor: "transparent",
},
ticks: {
padding: 20,
beginAtZero: true,
fontColor: "rgba(0,0,0,0.5)",
fontStyle: "bold"
}
}]
}
}
}
)
}
.HTML
<div class="row my-2">
<div class="col-md-6">
<canvas id=”myChart” #myChart height="130"></canvas>
</div>
</div>
HTML Canvas' createLinearGradient() depends on the y axis coordinates that you pass in as argument. You had passed in a static 200 every time (i.e. ctx.createLinearGradient(0, 200, 0, 20);).
That's why the gradient's steps remains the same everytime. For the gradient to update, you have to recalculate the height of the <canvas> element on window resize and pass it in to createLinearGradient() again.
You can accomplish this by:
Separating the block where you create the gradient into a separate function. eleHeight retrieves the height of the canvas element.
generateGradient(){
let eleHeight = this.myChart.nativeElement.offsetHeight;
// console.log(eleHeight)
let purple_orange_gradient: CanvasGradient = this.myChart.nativeElement.getContext('2d').createLinearGradient(0, eleHeight, 0, 20);
purple_orange_gradient.addColorStop(0.1, "#000279");
purple_orange_gradient.addColorStop(0.2, "#0000F2");
purple_orange_gradient.addColorStop(0.3, "#0362FD");
purple_orange_gradient.addColorStop(0.4, "#04D3FD");
purple_orange_gradient.addColorStop(0.5, "#45FFB7");
purple_orange_gradient.addColorStop(0.6, "#B7FF46");
purple_orange_gradient.addColorStop(0.7, "#FFD401");
purple_orange_gradient.addColorStop(0.8, "#FE6500");
purple_orange_gradient.addColorStop(0.9, "#F30004");
purple_orange_gradient.addColorStop(1, "#7E0100");
return purple_orange_gradient;
}
Add a onresize event handler to your containing <div> and generate the gradient again. You also need to programatically update the chart every time you make a change to re-render it.
<div style="display: block; max-height: 100%" (window:resize)="onResize($event)" >
...
</div>
onResize(event?){
// console.log("onResize");
this.barChartData.forEach((d, i) => {
d.backgroundColor = this.generateGradient();
})
this.chart.chart.update(); //update the chart to re-render it
}
Update the barchartData's properties (that uses gradient) in ngAfterViewInit. We need to do this here because we only want the height of the <canvas> element with data populated. Without data populated, the element is much smaller.
ngAfterViewInit(){
this.barChartData.forEach((d, i) => {
d.backgroundColor = this.generateGradient();
});
this.chart.chart.update(); //update the chart to re-render it
}
Have a look at this Stackblitz example⚡⚡ I have created.
You have to change the gradient whenever your canvas is resizing. Took me a while to figure out a good structure to minimize lines of code and optimize performance. This is the best I could achieve.
There are exeptions when the chart.js onResize() fires though but I couldn't solve this issue completly bulletproof. But for simple resizes it should work.
Complete code (same code in JSBin with live preview):
let sData = {}
sData.labels = []
sData.data = []
const count = 50
for (let x = 0; x < count; x++) {
sData.data.push(Math.floor(Math.random()*100))
sData.labels.push(x)
}
const canvas = document.getElementById('chart')
const ctx = canvas.getContext("2d")
let purple_orange_gradient
function updateGradient() {
let bottom = bar_chart.chartArea.bottom
let top = bar_chart.chartArea.top
purple_orange_gradient = ctx.createLinearGradient(0, bottom+top, 0, top)
purple_orange_gradient.addColorStop(0.1, "#000279")
purple_orange_gradient.addColorStop(0.2, "#0000F2")
purple_orange_gradient.addColorStop(0.3, "#0362FD")
purple_orange_gradient.addColorStop(0.4, "#04D3FD")
purple_orange_gradient.addColorStop(0.5, "#45FFB7")
purple_orange_gradient.addColorStop(0.6, "#B7FF46")
purple_orange_gradient.addColorStop(0.7, "#FFD401")
purple_orange_gradient.addColorStop(0.8, "#FE6500")
purple_orange_gradient.addColorStop(0.9, "#F30004")
purple_orange_gradient.addColorStop(1.0, "#7E0100")
return purple_orange_gradient
}
const bar_chart = new Chart(ctx, {
type: "horizontalBar",
data: {
labels: sData.labels,
datasets: [{
borderColor: purple_orange_gradient,
pointBorderColor: purple_orange_gradient,
pointBackgroundColor: purple_orange_gradient,
pointHoverBackgroundColor: purple_orange_gradient,
pointHoverBorderColor: purple_orange_gradient,
pointBorderWidth: 10,
pointHoverRadius: 10,
pointHoverBorderWidth: 1,
pointRadius: 3,
fill: true,
backgroundColor: purple_orange_gradient,
borderWidth: 4,
data: sData.data
}]
},
options: {
legend: {
display: false,
position: "bottom"
},
scales: {
yAxes: [{
ticks: {
display: false,
fontColor: "rgba(0,0,0,0.5)",
fontStyle: "bold",
beginAtZero: true,
maxTicksLimit: 1,
padding: 20,
},
gridLines: {
drawTicks: false,
display: false
}
}],
xAxes: [{
gridLines: {
zeroLineColor: "transparent",
},
ticks: {
padding: 20,
beginAtZero: true,
fontColor: "rgba(0,0,0,0.5)",
fontStyle: "bold"
}
}]
},
onResize: function(chart, size) {
// onResize gradient change
changeGradient()
}
}
});
// Initial gradient change
changeGradient()
function changeGradient() {
let newGradient = updateGradient()
bar_chart.data.datasets[0].borderColor = newGradient
bar_chart.data.datasets[0].pointBorderColor = newGradient
bar_chart.data.datasets[0].pointBackgroundColor = newGradient
bar_chart.data.datasets[0].pointHoverBackgroundColor = newGradient
bar_chart.data.datasets[0].pointHoverBorderColor = newGradient
bar_chart.data.datasets[0].backgroundColor = newGradient
bar_chart.update()
}
I wanted to stream live data in the form of a chart. I'm new to Javascript, so I wanted to first experiment with the sample on this page.
https://web.archive.org/web/20211113012042/https://nagix.github.io/chartjs-plugin-streaming/latest/samples/charts/line-horizontal.html
The code is given as:
var chartColors = {
red: 'rgb(255, 99, 132)',
orange: 'rgb(255, 159, 64)',
yellow: 'rgb(255, 205, 86)',
green: 'rgb(75, 192, 192)',
blue: 'rgb(54, 162, 235)',
purple: 'rgb(153, 102, 255)',
grey: 'rgb(201, 203, 207)'
};
function randomScalingFactor() {
return (Math.random() > 0.5 ? 1.0 : -1.0) * Math.round(Math.random() * 100);
}
function onRefresh(chart) {
chart.config.data.datasets.forEach(function(dataset) {
dataset.data.push({
x: Date.now(),
y: randomScalingFactor()
});
});
}
var color = Chart.helpers.color;
var config = {
type: 'line',
data: {
datasets: [{
label: 'Dataset 1 (linear interpolation)',
backgroundColor: color(chartColors.red).alpha(0.5).rgbString(),
borderColor: chartColors.red,
fill: false,
lineTension: 0,
borderDash: [8, 4],
data: []
}, {
label: 'Dataset 2 (cubic interpolation)',
backgroundColor: color(chartColors.blue).alpha(0.5).rgbString(),
borderColor: chartColors.blue,
fill: false,
cubicInterpolationMode: 'monotone',
data: []
}]
},
options: {
title: {
display: true,
text: 'Line chart (hotizontal scroll) sample'
},
scales: {
xAxes: [{
type: 'realtime'
}],
yAxes: [{
scaleLabel: {
display: true,
labelString: 'value'
}
}]
},
tooltips: {
mode: 'nearest',
intersect: false
},
hover: {
mode: 'nearest',
intersect: false
},
plugins: {
streaming: {
duration: 20000,
refresh: 1000,
delay: 2000,
onRefresh: onRefresh
}
}
}
};
window.onload = function() {
var ctx = document.getElementById('myChart').getContext('2d');
window.myChart = new Chart(ctx, config);
};
document.getElementById('randomizeData').addEventListener('click', function() {
config.data.datasets.forEach(function(dataset) {
dataset.data.forEach(function(dataObj) {
dataObj.y = randomScalingFactor();
});
});
window.myChart.update();
});
var colorNames = Object.keys(chartColors);
document.getElementById('addDataset').addEventListener('click', function() {
var colorName = colorNames[config.data.datasets.length % colorNames.length];
var newColor = chartColors[colorName];
var newDataset = {
label: 'Dataset ' + (config.data.datasets.length + 1),
backgroundColor: color(newColor).alpha(0.5).rgbString(),
borderColor: newColor,
fill: false,
lineTension: 0,
data: []
};
config.data.datasets.push(newDataset);
window.myChart.update();
});
document.getElementById('removeDataset').addEventListener('click', function() {
config.data.datasets.pop();
window.myChart.update();
});
document.getElementById('addData').addEventListener('click', function() {
onRefresh(window.myChart);
window.myChart.update();
});
<head>
<script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.22.2/moment.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.7.2/Chart.min.js"></script>
<script src="https://github.com/nagix/chartjs-plugin-streaming/releases/download/v1.5.0/chartjs-plugin-streaming.min.js"></script>
</head>
<body>
<div>
<canvas id="myChart"></canvas>
</div>
<p>
<button id="randomizeData">Randomize Data</button>
<button id="addDataset">Add Dataset</button>
<button id="removeDataset">Remove Dataset</button>
<button id="addData">Add Data</button>
</p>
</body>
When I copy and paste it into jsfiddle, the first code snippet going into the Javascript section and the second going into the HTML section. However, nothing happens? Could someone explain why/help me edit it so that it works?
Note: the code above is not my own, it belongs to this guy
In JSFiddle, the load type is set to 'On Load' by default, so you cannot handle the load event. Setting the load type to 'No wrap - bottom of ' works (in the pop-up menu in the Javascript section).
In my controller I have an Action method that will find all questions in a table called Questions, and the answers for each question.
This Action is of type ContentResult that will return a result serialized in Json format.
public ContentResult GetData()
{
var datalistQuestions = db.Questions.ToList();
List<PsychTestViewModel> questionlist = new List<PsychTestViewModel>();
List<PsychTestViewModel> questionanswerslist = new List<PsychTestViewModel>();
PsychTestViewModel ptvmodel = new PsychTestViewModel();
foreach (var question in datalistQuestions)
{
PsychTestViewModel ptvm = new PsychTestViewModel();
ptvm.QuestionID = question.QuestionID;
ptvm.Question = question.Question;
questionlist.Add(ptvm);
ViewBag.questionlist = questionlist;
var agree = //query
var somewhatAgree = //query
var disagree = //query
int Agree = agree.Count();
int SomewhatAgree = somewhatAgree.Count();
int Disagree = disagree.Count();
ptvmodel.countAgree = Agree;
ptvmodel.countSomewhatAgree = SomewhatAgree;
ptvmodel.countDisagree = Disagree;
questionanswerslist.Add(ptvmodel);
ViewBag.questionanswerslist = questionanswerslist;
}
return Content(JsonConvert.SerializeObject(ptvmodel), "application/json");
}
Now, my problem is the pie chart is not being created and I don't quite know how to push the values to my data structure?
What should I be doing instead?
Here is my script:
#section Scripts {
<script type="text/javascript">
var PieChartData = {
labels: [],
datasets: [
{
label: "Agree",
backgroundColor:"#f990a7",
borderWidth: 2,
data: []
},
{
label: "Somewhat Agree",
backgroundColor: "#aad2ed",
borderWidth: 2,
data: []
},
{
label: "Disgree",
backgroundColor: "#9966FF",
borderWidth: 2,
data: []
},
]
};
$.getJSON("/PsychTest/GetData/", function (data) {
for (var i = 0; i <= data.length - 1; i++) {
PieChartData.datasets[0].data.push(data[i].countAgree);
PieChartData.datasets[1].data.push(data[i].countSomewhatAgree);
PieChartData.datasets[2].data.push(data[i].countDisagree);
}
var ctx = document.getElementById("pie-chart").getContext("2d");
var myLineChart = new Chart(ctx,
{
type: 'pie',
data: PieChartData,
options:
{
responsive: true,
maintainaspectratio: true,
legend:
{
position : 'right'
}
}
});
});
</script>
You need two arrays for creating your chart. One of them indicates titles and another one shows the number of each titles. You have titles in the client side, so you only need the number of each options and it could be fetched from a simple server method like:
[HttpGet]
public JsonResult Chart()
{
var data = new int[] { 4, 2, 5 }; // fill it up whatever you want, but the number of items should be equal with your options
return JsonConvert.SerializeObject(data)
}
The client side code is here:
var aLabels = ["Agree","Somewhat Agree","Disagree"];
var aDatasets1 = [4,2,5]; //fetch these from the server
var dataT = {
labels: aLabels,
datasets: [{
label: "Test Data",
data: aDatasets1,
fill: false,
backgroundColor: ["rgba(54, 162, 235, 0.2)", "rgba(255, 99, 132, 0.2)", "rgba(255, 159, 64, 0.2)", "rgba(255, 205, 86, 0.2)", "rgba(75, 192, 192, 0.2)", "rgba(153, 102, 255, 0.2)", "rgba(201, 203, 207, 0.2)"],
borderColor: ["rgb(54, 162, 235)", "rgb(255, 99, 132)", "rgb(255, 159, 64)", "rgb(255, 205, 86)", "rgb(75, 192, 192)", "rgb(153, 102, 255)", "rgb(201, 203, 207)"],
borderWidth: 1
}]
};
var opt = {
responsive: true,
title: { display: true, text: 'TEST CHART' },
legend: { position: 'bottom' },
//scales: {
// xAxes: [{ gridLines: { display: false }, display: true, scaleLabel: { display: false, labelString: '' } }],
// yAxes: [{ gridLines: { display: false }, display: true, scaleLabel: { display: false, labelString: '' }, ticks: { stepSize: 50, beginAtZero: true } }]
//}
};
var ctx = document.getElementById("myChart").getContext("2d");
var myNewChart = new Chart(ctx, {
type: 'pie',
data: dataT,
options: opt
});
<script src="https://github.com/chartjs/Chart.js/releases/download/v2.7.1/Chart.min.js"></script>
<div Style="font-family: Corbel; font-size: small ;text-align:center " class="row">
<div style="width:100%;height:100%">
<canvas id="myChart" style="padding: 0;margin: auto;display: block; "> </canvas>
</div>
</div>
If you are still looking to use json for chart.js charts.
Here is a solution which fetch a json file and render it on chart.js chart.
fetch('https://s3-us-west-2.amazonaws.com/s.cdpn.io/827672/CSVtoJSON.json')
.then(function(response) {
return response.json();
})
.then(function(ids) {
new Chart(document.getElementById("bar-chart"), {
type: 'bar',
data: {
labels: ids.map(function(id) {
return id.Label;
}),
datasets: [
{
label: "value2",
backgroundColor: ["#3e95cd", "#8e5ea2","#3cba9f","#e8c3b9","#c45850"],
data: ids.map(function(id) {
return id.Value2;
}),
},
{
label: "value",
//backgroundColor: ["#3e95cd", "#8e5ea2","#3cba9f","#e8c3b9","#c45850"],
data: ids.map(function(id) {
return id.Value;
}),
},
]
},
options: {
legend: { display: false },
title: {
display: true,
text: 'Sample Json Data Chart'
}
}
});
});
see running code on jsfiddle here
I created a radar chart in chart.js. How do I update the chart with numbers the user specifies with a drop down menu? I created a variable for each input as follows: "spaceScore", "styleScore", "scheduleScore", "supplementScore".
$(document).ready(function(){
"use strict";
new Chart(document.getElementById("radarChart"), {
type: 'radar',
data: {
labels: ["Space", "Style", "Schedule", "Supplement"],
datasets: [
{
label: "Cognizant Baseline",
fill: false,
backgroundColor: "rgba(179,181,198,0.2)",
borderColor: "rgba(179,181,198,1)",
pointBorderColor: "#fff",
pointBackgroundColor: "rgba(179,181,198,1)",
data: [1,3,1,2]
}, {
label: "Assessment",
fill: true,
backgroundColor: "rgba(255,99,132,0.2)",
borderColor: "rgba(255,99,132,1)",
pointBorderColor: "#fff",
pointBackgroundColor: "rgba(255,99,132,1)",
data: ['spaceScore','styleScore','scheduleScore','supplementScore']
}, {
label: "Learner Centricity",
fill: true,
backgroundColor: "rgba(114, 205, 244,0.2)",
borderColor: "rgba(114, 205, 244,1)",
pointBorderColor: "#fff",
pointBackgroundColor: "rgba(114, 205, 244,1)",
data: [2,2,2,1]
}
]
},
options: {
title: {
display: false,
},
legend: {
display: false
},
tooltips: {
enabled: false
}
}
});
function getData(){
var radarChart = document.getElementById("radarChart");
var spaceScore = document.getElementById('spaceScore').value();
var styleScore = document.getElementById('styleScore').value;
var scheduleScore = document.getElementById('scheduleScore').value;
var supplementScore = document.getElementById('supplementScore').value;
radarChart.update;
}
});
I added 4 number inputs as an interface to update values. I gave them values ranging from 0 to 3, adapt to your needs. I also added an update button, so that the update happens only when you click it.
If you want specifically drop-down inputs, just replace the number inputs with traditional <select> tags, with <options> matching possible values.
To perform the actual update on the chart you need to first overwrite the old data from the dataset, then call a rerendering of the char-canvas with radarChart.update(). Follow the inline code comments to get an idea of whats happening in code.
$(document).ready(function() {
"use strict";
// hold a radarChart reference for future updates
var radarChart = new Chart(document.getElementById("radarChart"), {
type: 'radar',
data: {
labels: ["Space", "Style", "Schedule", "Supplement"],
datasets: [{
label: "Cognizant Baseline",
fill: false,
backgroundColor: "rgba(179,181,198,0.2)",
borderColor: "rgba(179,181,198,1)",
pointBorderColor: "#fff",
pointBackgroundColor: "rgba(179,181,198,1)",
data: [1, 3, 1, 2]
}, {
label: "Assessment",
fill: true,
backgroundColor: "rgba(255,99,132,0.2)",
borderColor: "rgba(255,99,132,1)",
pointBorderColor: "#fff",
pointBackgroundColor: "rgba(255,99,132,1)",
data: ['spaceScore', 'styleScore', 'scheduleScore', 'supplementScore']
}, {
label: "Learner Centricity",
fill: true,
backgroundColor: "rgba(114, 205, 244,0.2)",
borderColor: "rgba(114, 205, 244,1)",
pointBorderColor: "#fff",
pointBackgroundColor: "rgba(114, 205, 244,1)",
data: [2, 2, 2, 1]
}]
},
options: {
title: {
display: false,
},
legend: {
display: false
},
tooltips: {
enabled: false
}
}
});
// click handler of the update button
$('#update').on('click', function() {
getData();
});
function getData() {
// get new user-selected values
var spaceScore = document.getElementById('spaceScore').value;
var styleScore = document.getElementById('styleScore').value;
var scheduleScore = document.getElementById('scheduleScore').value;
var supplementScore = document.getElementById('supplementScore').value;
// update chart dataset with new values
radarChart.data.datasets[0].data[0] = spaceScore;
radarChart.data.datasets[0].data[1] = styleScore;
radarChart.data.datasets[0].data[2] = scheduleScore;
radarChart.data.datasets[0].data[3] = supplementScore;
// redraw chart
radarChart.update();
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.6.0/Chart.bundle.js"></script>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div class="inputs">
<input id="spaceScore" type="number" min="0" max="3" value="1" />
<input id="styleScore" type="number" min="0" max="3" value="3" />
<input id="scheduleScore" type="number" min="0" max="3" value="1" />
<input id="supplementScore" type="number" min="0" max="3" value="2" />
<button id="update" type="button">Update</button>
</div>
<canvas id="radarChart" />
I got a chart from Chart JS library.
Screenshot
var ctx = document.getElementById("myChart");
var data = {
labels: ["HTML", "CSS", "JavaScript", "jQuery", "Bootstrap", "Gulp", "PHP", 'SQL', 'Git'],
datasets: [
{
defaultFontColor: 'red',
backgroundColor: "rgba(0,255,255,.4)",
borderColor: "rgba(0,255,255,.4)",
pointBackgroundColor: "red",
pointBorderColor: "#fff",
lineTension: 0,
pointHoverBackgroundColor: "#fff",
pointHoverBorderColor: "rgba(179,181,198,1)",
data: [95, 99, 60, 91, 36, 95, 40, 95, 95]
}
]
};
var myRadarChart = new Chart(ctx, {
type: 'radar',
data: data,
options: {
responsive: true,
scale: {
reverse: false,
ticks: {
// defaultFontSize: true
}
}
}
});
I need to change font styles for underlined labels. I've dug over documentation and i tried all what i could. Even global font settings didn't change label styles, though it worked for the rest of other text. Have you met such a problem? Thanks.
It's well hidden, but you can find this under "Point Label Options"
http://www.chartjs.org/docs/#scales-radial-linear-scale
here is a example:
https://jsfiddle.net/qvrt01jp/1/
options: {
scale: {
pointLabels :{
fontStyle: "bold",
}
}
}
global should also work if set it like this:
Chart.defaults.global.defaultFontStyle = 'italic'
To give an update for v3.5.1:
Like this for font weights:
Chart.defaults.font.weight = '600';
Or if you want to do it inside the options object:
options: {
plugins: {
legend: {
labels: {
font: {
style: 'italic',
weight: '600',
}
}
}
}
}
Documentation with more info: https://www.chartjs.org/docs/latest/general/fonts.html