Develop Reference

How can I create a dynamically assigned variable for a chart with chart.js?

I am trying to create a series of line chart dynamically and then update them once the data has been updated for a particular user in real-time.
I am running into difficulty because I can only get the most recent one to render.
I think this is because when the following code runs it overwrites the ctx variable and I lose the earlier charts.
I tried the following technique with dynamic variables so no two ctx variables would be the same, but it doesn't work.
Thanks in advance for your help.
window['ctx_'+userid] = document.getElementById("forceCurveGraph_"+userid).getContext("2d");
window['myLineChart'+userid] = new Chart(window['ctx_'+userid], {
type: 'line', data: {
datasets: [{
label: "Force Curve",
data: forcecurvedata, backgroundColor: ['rgba(57,118,251, 0.8)']
}],
labels: labels
}, options: {
backgroundColor: ['rgba(40, 84, 141, 0.3)'],
scales: {
yAxes: [{
ticks: {
beginAtZero: true,
max: graphMax
}
}],
xAxes: [{
ticks: {
display: false
}
}]
}
}
})

Chartjs-plugin-zoom plugin does not change x axis labels

I am working with the chart.js module in order to plot some data and am using the chartjs-plugin-zoom in order to enable zooming and panning however although the zooming works the labels on the x axis will not change for whatever reason.
I have seen similar questions but they all dealt with time series data and therefore the advice was unhelpful.
Here is the plot zoomed out:
and here is it zoomed in:
The key thing to notice is how the labels on the y axis have changed but the x axis labels have not changed. Here is the relevant config variable of the chart:
const config3 = {
type: 'line',
data: {
labels: [I ran out of chars but this is just a very long list of numbers in this format: 1,2,3,4,5],
datasets: [
{
label: "",
backgroundColor: '#'+Math.floor(Math.random()*16777215).toString(16),
borderColor: '#0071BC',
data: [I ran out of chars but this is just a very long list of numbers in this format: 1,2,3,4,5],
fill: false,
borderWidth: 1,
},
],
},
options: {
responsive: true,
title: {
display: true,
text: 'Peak: -1.2188'
},
tooltips: {
mode: 'index',
intersect: false,
},
hover: {
mode: 'nearest',
intersect: true
},
scales: {
xAxes: [{
display: true,
scaleLabel: {
display: true,
labelString: 'Frequency (Hz)'
},
ticks:{
autoSkip: true,
maxTicksLimit: 20
},
}],
yAxes: [{
display: true,
scaleLabel: {
display: true,
labelString: 'Amplitude'
}
}],
},
plugins:{
zoom: {
pan: {
enabled: true,
mode: 'xy',
speed: 20,
threshold: 10,
},
zoom: {
enabled: true,
drag: false,
mode: "xy",
speed: 0.1,
// sensitivity: 0.1,
}
}
},
elements: {
point:{
radius: 0
}
}
}
};
If needed I can provide more code but I imagine the mistake is probably contained in the config. I tried changing zoom.mode to be 'x' but that did not work.

In case someone else comes along this I figured out a solution that is pretty unintuitive.
The first problem is the way that labels are dealt with in chart.js and because they are treated as categories not x data the way that I thought they were. Therfore first you must pass your data in as coordinates in this format:
(as shown in this documentation: https://www.chartjs.org/docs/latest/charts/line.html)
data: [{
x: 10,
y: 20
}, {
x: 15,
y: 10
}]
And delete the labels variable.
However this will not work with line charts despite what the documentation says. To get around this you can set: type: 'scatter' and inside the dataset write showLine: true
This will generate a line plot where the x labels are auto generated and zooming will work perfectly.
I also think there was a performance boost which is a nice bonus.

ChartJS - How to increase the maximum degree of label rotation on x-axis?

I have a line chart, and at first, all the labels on x-axis are fully horizontal. Something like this:
Now if add more data, the labels start to rotate:
Until comes a point where it seems to have reached the maximum degree to which it can rotate:
By the looks of it, I think the maximum degree is 45. So now, if I add a little more data, instead of rotating the labels more, it removes every one in two labels, and becomes like this:
How can I increase this degree to 90, so that the labels rotate as much as becoming fully vertical?
Here's the code I used for the chart:
new Chart(chart, {
type: 'line',
data: chart_data,
options: {
scales: {
yAxes: [{
ticks: {
beginAtZero: false
}
}]
},
legend: {
position: 'top',
labels: {
boxWidth: 5,
usePointStyle: true
}
},
events: ['click', 'mousemove'],
onClick: clicked,
pan: {
enabled: true,
mode: 'x',
onPanComplete: function(event) {
console.log(event)
}
},
zoom: {
enabled: true,
mode: 'x'
}
}
});

You can configure this using the maxRotation property of the common tick configuration object.
Your code needs to be modified like so:
options: {
scales: {
xAxes: [{
ticks: {
maxRotation: 90
}
}],
yAxes: [{
...

The keyword of the issue is not rotation i think, it is Tick on xAxes.
I think this link can help you :
https://www.chartjs.org/docs/latest/axes/styling.html#tick-configuration
also
Chart.js: evenly distribute ticks when using maxTicksLimit
xAxes: [{
ticks: {
autoSkip: false, // Skip or not?
maxTicksLimit: 30 // How much?
}
}]
and rotation just can help as #timclutton said here : https://stackoverflow.com/a/58275468/7514010

Chart.js mixed chart : Lines not starting at zero

current situation
chart
what i want : chart
I build a mixed chart with lines and bars. I have problem with lines.
Lines not starting at zero.
Here is my codes;
https://jsfiddle.net/ameydan/vb4fsyqp/31/
` options: {
legend: {
display: false,
position: 'top',
},
elements: {
point: {
radius: 0
}
},
scales: {
yAxes: [{
stacked: true,
ticks: {
beginAtZero: true
}
}
],
xAxes: [{
stacked: true,
ticks: {
beginAtZero: true
}
}
]
}
}`
thanks in advance.
beginAtZero : true , not solved problem.

That is cause you setted stacked to true.
scales: {
yAxes: [{
stacked: **false**,
ticks: {
beginAtZero: true
}
}
],
xAxes: [{
stacked: true,
ticks: {
beginAtZero: true
}
}
]
}
EDIT:
Second thought coming from => https://www.chartjs.org/docs/latest/charts/mixed.html
At this point we have a chart rendering how we'd like. It's important to note that the default options for a line chart are not merged in this case. Only the options for the default type are merged in. In this case, that means that the default options for a bar chart are merged because that is the type specified by the type field.
I found a solution!
Just add this :
myChart.options.scales.xAxes[0].offset = false;
myChart.update();
The only counterpart is that if there's data # index 0 of a bar dataset, it will be only half drawn and the last one as well as shown here : https://jsfiddle.net/0qsh8znu/1/

I had the same issue. When I followed #rOulito 's solution, I found that the lack of offset for my line graph made it no longer line up with the data points of my bar graph, so that didn't work, sadly.
My solution was to follow the docs for a chartjs plugin for annotations
This is how I drew a line from the first data point of my line graph to the bottom left of the graph:
let options = {
plugins: {
annotation: {
annotations: {
line1: {
type: 'line',
yMax: 50000,
xMax: 0,
borderColor: 'black',
borderWidth: 3,
},
},
},
},
};

How to remove the line/rule of an axis in Chart.js?

I managed to remove all horizontale lines/rules in my chart using this:
scales: {
xAxes: [{
gridLines: {
display: false
}
}]
}
But I also want to get rid of the rule/bar that represents the Y-axis as well. But I want to keep the labels:
Unfortunately I can't find any option for that. I can only remove the whole axis including labels.
I'm using Chart.js 2.3.

I found a way to remove this line. It's actually called the border of the axis and there's an option for it, see "Grid Line Configuration":
scales: {
yAxes: [{
gridLines: {
drawBorder: false,
}
}]
}

This should work
options: {
scales: {
yAxes: [{
gridLines: {
display: false,
}
}]
},
}

This worked for me in version 2.8.0 -
scales: {
yAxes: [{
gridLines: {
tickMarkLength: false,
}
}]
}

In v3 you can do:
options: {
scales: {
y: {
grid: {
drawBorder: false,
}
}
}
}
https://www.chartjs.org/docs/master/axes/styling#grid-line-configuration

The left line is still coming from the x axis grid lines. Changing the 'zeroLineColor' of the x axis to 'transparent' hid it.
xAxes:[{
gridLines:{
zeroLineColor:'transparent'
}}]
Source: https://github.com/chartjs/Chart.js/issues/3950

gridLines: {zeroLineColor: 'transparent'}

this workerd for me
yAxes: [ { gridLines: { display: false, }, }, ],

You can use the scaleLineColor: 'transparent' it will remove the y any x axis