Outlier slows down zooming in scattergl
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- Dominant language
- JavaScript
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Description
I have large data sets, which have a fat tail, i.e. looks like having an outlier.
I use scattergl aiming for fast zooming. As shown in https://plotly.com/javascript/webgl-vs-svg
or in the example below, one million points can be done. However, if one point is set as an outlier, then zooming becomes very
slow. I don't understand this, and spent quite some time to pin down the problem.
<!DOCTYPE html>
<html>
<div id="plotly-div1"></div>
<div id="plotly-div2"></div>
<script src='https://cdn.plot.ly/plotly-latest.min.js'></script>
<script>
function gaussianRand() {
var rand = 0
for (var i=0; i < 3; ++i) {
rand += Math.random()
}
return (rand / 3) - 0.5
}
function plot(y, divnum){
trace1 = {
type: "scattergl",
y: y,
}
layout = {
height: 250,
margin: {l: 40, r: 10, b: 30, t: 10}
}
Plotly.plot('plotly-div'+divnum, {
data: [trace1],
layout: layout,
})
}
Y = []
for (var i=0; i < 1000000; i++) {
Y.push(gaussianRand())
}
plot(Y, 1)
Y[800000] = 100. // adding an outlier slows down zoom
plot(Y, 2)
delete Y
</script>
</html>
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by running the linked JSFiddle reproduction and compare zooming for the million-point scattergl data with and without the single outlier. Investigate the scattergl zoom path and WebGL behavior implicated by the example. Done means zooming performance no longer degrades substantially when one outlier is present.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript
- Domain
- data-visualization, performance
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100