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mzechmeister opened this issue Apr 30, 2022 · 3 comments
Open

Outlier slows down zooming in scattergl #6174

mzechmeister opened this issue Apr 30, 2022 · 3 comments
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bug something broken P3 backlog

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@mzechmeister
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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.

https://jsfiddle.net/fasmu943

<!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>
@alexcjohnson
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Thanks for digging in to this @mzechmeister - I suspect this case is problematic for our clustering algorithm for hover

plotly.js/src/traces/scattergl/calc.js

Line 78 in 042742d

stash.tree = cluster(positions);

@mzechmeister
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Thanks for looking into the issue and the hover hint.
When setting hovermode: false in layout, then the zoom speed feels similar both cases. That helps for now.

@CallumNZ
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Contributor

I'm running into a similar problem. Some examples from one data set:

Range: 04-Feb to 21-Feb
Points: 103066
Lag on zoom? YES

image

Range: 04-Feb to 21-Feb, removing points from the middle that were outliers/not showing the same wave pattern.
Points: 85165
Lag on zoom? YES

image

Range: 06-Feb to 21-Feb
Points: 91866
Lag on zoom? NO

image

Range: 01-Feb to 17-Feb
Points: 97920
Lag on zoom? NO

image

Range: 01-Feb to 18-Feb
Points: 103680
Lag on zoom? YES

image

Setting hover mode: false as a workaround works as mentioned above.

@CmpCtrl CmpCtrl mentioned this issue Jun 23, 2024
Open
@gvwilson gvwilson self-assigned this Jul 4, 2024
@gvwilson gvwilson removed their assignment Aug 2, 2024
@gvwilson gvwilson added bug something broken P3 backlog labels Aug 9, 2024
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@gvwilson @alexcjohnson @CallumNZ @mzechmeister