I believe, what you are looking for, is a scatter graph, not line.
var x = new Chart(document.getElementById("myChart1"), {
type: 'scatter',
data: {
datasets: [{
label: "Test",
data: [{
x: 0,
y: 5
}, {
x: 5,
y: 10
}, {
x: 8,
y: 5
}, {
x: 15,
y: 0
}],
}]
},
options: {
responsive: true
}
});
<script src="https://cdnjs.cloudflare.com/ajax/libs/Chart.js/2.6.0/Chart.min.js"></script>
<canvas id="myChart1"></canvas>
Refer here, to learn more about scatter chart.