Add buffer to Y axis with chart js - chart.js

Question

Sometimes chart value is the same height as chart height. For example im my picture red bar is 6, the same as y-axis top number. Can I add some buffer so chart bar never reaches top of y axis? Lets say y axis would go to 7 now (or similar).
Image show my problem (open image in new window for better view)

Answer 1

By Axis Range Settings
https://www.chartjs.org/docs/latest/axes/cartesian/linear.html#axis-range-settings
suggestedMax: 7
1/2. Static max value example
Change min to 10 and max to 90 (For data[30, 40, 50, 60]).
let chart = new Chart(ctx, {
type: 'line',
responsive: true,
data: {
datasets: [{
label: 'First dataset',
data: [30, 40, 50, 60]
}],
labels: ['January', 'February', 'March', 'April']
},
options: {
scales: {
yAxes: [{
ticks: {
suggestedMin: 10,
suggestedMax: 90
}
}]
}
}
});
<canvas id="ctx" width="800" height="350"></canvas>
<script src="https://cdn.jsdelivr.net/npm/chart.js#2.8.0"></script>
2/2. Dynamic "buffer"
First no one solution for this idea (The max value related to your data structure). For the most basic data structure (Flat), this is one solution:
Get the max value of [20,40,60, 80] ==> 80
updateScaleDefaults Change max y-axis to max + buffer (20 in this example)
updateScaleDefaults - The default configuration for a scale can be easily changed using the
scale service. All you need to do is to pass in a partial
configuration that will be merged with the current scale default
configuration to form the new default. https://www.chartjs.org/docs/latest/axes/#updating-axis-defaults
Example:
For data: [20,40,60, 80]
/* data */
var data = {
labels: ["Africa", "Asia", "Europe", "America"],
datasets: [{
/* data */
label: "Population (millions)",
backgroundColor: ["#3e95cd", "#8e5ea2","#3cba9f", '#1d49b8'],
data: [20,40,60, 80]
}]
};
/* buffer trick */
var buffer = 20;
const dataSet = data.datasets[0].data;
console.log("data: " + dataSet);
/* https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Math/max */
var maxDATAvalue = Math.max(...dataSet);
var maxValuePlusBuffer = maxDATAvalue + buffer;
console.log("max value(" + maxDATAvalue + ") / Plus Buffer(" + maxValuePlusBuffer + ")");
/* The default configuration for a scale can be easily changed using the scale service. */
/* https://www.chartjs.org/docs/latest/axes/#updating-axis-defaults */
Chart.scaleService.updateScaleDefaults('linear', {
ticks: {
max: maxValuePlusBuffer
}
});
var options = {
responsive: true,
title: {
text: 'Set max value to max(data) + Buffer',
display: true
},
scales: {
xAxes: [{
stacked: true,
ticks: {
},
}],
yAxes: [{
stacked: true,
}]
}
};
var myChart = new Chart(document.getElementById("chart"), {
type: 'bar',
data: data,
options: options
});
<canvas id="chart" width="800" height="350"></canvas>
<script src="https://cdn.jsdelivr.net/npm/chart.js#2.8.0"></script>
Related Stackoverflow Q:
How to set max and min value for Y axis
ChartJS: How to set fixed Y axis max and min