Fix Jiffle sdev() returning the range instead of the standard deviation - #314
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james-willis wants to merge 1 commit into
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Fix Jiffle sdev() returning the range instead of the standard deviation#314james-willis wants to merge 1 commit into
james-willis wants to merge 1 commit into
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JiffleFunctions.sdev called SampleStats.range rather than SampleStats.sdev, so the Jiffle sdev() function returned the range of its input list. Fix the delegation and add tests: one asserting the sample standard deviation of a known list, one asserting sdev(z)^2 == variance(z).
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Bug
JiffleFunctions.sdevdelegates toSampleStats.rangeinstead ofSampleStats.sdev:so the Jiffle
sdev()script function actually returns the range of its input list, e.g.sdev([1, 2, 3, 4])returns3.0instead ofsqrt(5/3) ≈ 1.29099.variance()is unaffected (it correctly delegates toSampleStats.variance).Fix
One-line delegation fix, plus two new tests in
StatsFunctionsTest:sdevListArgasserts the sample standard deviation of a fixed list, andsdevIsSquareRootOfVarianceassertssdev(z)*sdev(z) == variance(z)per pixel.mvn -pl jt-jiffle/jt-jiffle-language testpasses (291 tests) under JDK 8.Compatibility note
Any script relying on the buggy behavior will see different results after this fix;
range()remains available for callers who actually want the range.