fix(computeStats) #427 Exception thrown when firstQuartile and thirdQuartile are equal

[LethalPants]

🐛 Bug Fix

• Fixes Exception thrown when firstQuartile and thirdQuartile are equal in @vx/stats/computeStats #427 by changing method to calculate firstQuartile and thirdQuartile

Test result

[coveralls]

Pull Request Test Coverage Report for Build 290721624

• 10 of 10 (100.0%) changed or added relevant lines in 1 file are covered.
• 12 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.9%) to 56.697%

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Files with Coverage Reduction	New Missed Lines	%
packages/visx-xychart/src/components/XYChart.tsx	2	92.5%
packages/visx-xychart/src/components/series/BarSeries.tsx	5	58.44%
packages/visx-xychart/src/components/series/LineSeries.tsx	5	41.38%

Totals
Change from base Build 82:	0.9%
Covered Lines:	1250
Relevant Lines:	2128

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💛 - Coveralls

[williaster]

Hey @LethalPants thanks for the fix AND the test 🚀 ! I had one suggestion but otherwise looks good.

[hshoff]

One thing that tripped me up on this is computeStates(data).boxPlot.min and computeStates(data).boxPlot.max are not the min/max value in the dataset but the the low (Q₁ - 1.5 * IQR) & high (Q₃ + 1.5 * IQR) values which are used for calculating the outliers and are the min/max when showing outliers. But when there are no outliers min/max should be the Math.min(data) and Math.max(data).

For example:

data = [10000, 2400, 10000, 10000]
computeStats(data).boxPlot;
{
  "min": 500,
  "firstQuartile": 6200,
  "median": 10000,
  "thirdQuartile": 10000,
  "max": 15700,
  "outliers": []
}

The expected output should be

{
  "min": 2400,
  "firstQuartile": 6200,
  "median": 10000,
  "thirdQuartile": 10000,
  "max": 10000,
  "outliers": []
}

No need to fix this here with this PR, but wanted to flag it as I stumbled on this while reviewing.

[williaster]

thanks again @LethalPants, looks good.

I created #851 to track the min/max issue @hshoff noted.