observablehq / observablehq/plot
Interval scale produces wrong ticks and labels
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Description
According to Observable Plot docs, interval scale can take numbers:
The option can also be specified as a number, in which case it will be promoted to a numeric interval with the given step.
In the following example, I apply an interval transform and an interval scale (both given by a number) to pre-binned data. Resulting plot has wrong x-axis ticks and labels.
Example
See also Observable Notebook.
Given data (already binned with bin width 0.05 or bin step -20)
data = [
{ "x": 0.15, "y": 1 },
{ "x": 0.25, "y": 5 },
{ "x": 0.35, "y": 85 },
{ "x": 0.4, "y": 196 },
{ "x": 0.45, "y": 268 },
{ "x": 0.5, "y": 380 },
{ "x": 0.55, "y": 354 },
{ "x": 0.6, "y": 658 },
{ "x": 0.65, "y": 7382 },
{ "x": 0.7, "y": 45588 },
{ "x": 0.75, "y": 67028 },
{ "x": 0.8, "y": 52965 },
{ "x": 0.9, "y": 95069 },
{ "x": 0.95, "y": 30982 }
]
With Interval transform, but without Interval scale
Plot.plot({
marks: [
Plot.rectY(data, { x: "x", y: "y", interval: 0.05 })
]
})
This looks good. Now, I want to add an interval scale:
With Interval transform, with Interval scale
Plot.plot({
x: {
interval: 0.05
},
marks: [
Plot.rectY(data, { x: "x", y: "y", interval: 0.05 })
]
})
This plot has a wrong x-axis:
- Ticks are off by 0.05
- 0.3 and 0.8 are each shown twice
- 0.2 and 0.4 are missing
Increasing the number of ticks produces a correct plot:
With Interval transform, with Interval scale, and with explicit ticks
Plot.plot({
x: {
interval: 0.05,
ticks: 18
},
marks: [
Plot.rectY(data, { x: "x", y: "y", interval: 0.05 })
]
})
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 with the x-axis interval-scale handling and tick generation used by the Plot.plot configuration in the example. Reproduce the supplied pre-binned data case, then verify that interval 0.05 produces correctly positioned, non-duplicated ticks and labels both with default ticks and with explicit ticks.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript
- Domain
- data-visualization
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100