Hi, When I was drawing the bin transform and calculating the proportion information of each bin, I found that some values were negative. Why are there negative values? Should the proportion not always be greater than 0?

My code is as follows:

```
Plot.plot({
height: 200,
width: 840,
// marginLeft: 85,
x: { domain: this.x },
// y: { axis: null },
// x: { nice: true },
// fy: { domain: this.cells }, // excludes N/A
color: { range: this.colorRange, domain: colorArr },
facet: { data: data },
marks: [
Plot.areaY(
data,
Plot.binX(
{ y2: "proportion" }, // using y2 to avoid areaY’s implicit stacking
{
x: "vae_x",
fill: this.colored,
fillOpacity: 0.1,
thresholds: 10,
curve: "natural",
}
)
),
Plot.ruleY([0]),
Plot.lineY(
data,
Plot.binX(
{ y: "proportion" },
{
x: "vae_x",
// y: "vae_y",
stroke: this.colored,
thresholds: 10,
curve: "natural",
}
)
),
Plot.axisX({
tickSpacing: 50,
label: null,
}),
Plot.axisY({
tickSpacing: 50,
label: null,
}),
],
});
```

Thanks very much to the kind stranger!