simplest way to update data in VegaEmbed - vega-lite

Question

I made a small graph to show some data from a bluetooth device.
I used a sample I found for VegaEmbed, it was all very easy.
But the sample uses a timer to get data, so even if there is no data the dataset will be changed. What is the simples way to update data inside VegaEmbed from another part of the website ?
I cannot call res.view.change('table', changeSet).run(); from outside VegaEmbded..
Here is snappshot of the code :
(the function handleDataChanged is called when there is bluetooth data.)
function handleDataChanged(event) {
var value = event.target.value;
value = value.buffer ? value : new DataView(value);
let result = {};
let index = 1;
datapointx = value.getInt16(index, /*littleEndian=*/false);
console.log('X: ' + value.getInt16(index, /*littleEndian=*/false));
index += 2;
datapointy = value.getInt16(index, /*littleEndian=*/true);
console.log('Y: ' + value.getInt16(index, /*littleEndian=*/false));
index += 2;
datapointz = value.getInt16(index, /*littleEndian=*/true);
console.log('Z: ' + value.getInt16(index, /*littleEndian=*/false));
index += 2;
}
</script>
<script>
document.querySelector('button').addEventListener('click', function() {
onButtonClick();
});
</script>
<script type="text/javascript">
var vlSpec = {
$schema: 'https://vega.github.io/schema/vega-lite/v3.json',
data: {name: 'table'},
width: 400,
mark: 'line',
encoding: {
x: {field: 'x', type: 'quantitative', scale: {zero: false}},
y: {field: 'y', type: 'quantitative'},
color: {field: 'category', type: 'nominal'}
}
};
vegaEmbed('#chart', vlSpec).then(function(res) {
/**
* Generates a new tuple with random walk.
*/
function newGenerator() {
var counter = -1;
var previousY = [5, 5, 5];
return function() {
counter++;
var newVals = previousY.map(function(v, c)
{
console.log('c = ' + c);
var yval = 0;
if (c == 0)
yval = datapointx;
if (c == 1)
yval = datapointy;
if (c == 2)
yval = datapointz;
return {
x: counter,
// y: v + Math.round(Math.random() * 10 - c * 3),
y: yval,
category: c
};
});
previousY = newVals.map(function(v) {
return v.y;
});
return newVals;
};
}
var valueGenerator = newGenerator();
var minimumX = -100;
window.setInterval(function() {
minimumX++;
var changeSet = vega
.changeset()
.insert(valueGenerator())
.remove(function(t) {
return t.x < minimumX;
});
res.view.change('table', changeSet).run();
}, 100);
});
</script>

Answer 1

The simplest way to update data in an existing vega-lite chart is to use a streaming data model. There is an example in the Vega-Lite documentation here: https://vega.github.io/vega-lite/tutorials/streaming.html