R devel - Jun 2019 - Small bug in fligner.test - constant values can produce significant results (patch attached)

In specific cases fligner.test() can produce a small p-value even when both
groups have constant variance.

Here is an illustration:

    fligner.test(c(1,1,2,2),
c("a","a","b","b"))
    # p-value = NA

But:

    fligner.test(c(1,1,1,2,2,2),
c("a","a","a","b","b","b"))
    # p-value < 2.2e-16

This can potentially get dangerous if people perform lots of parallel tests of
this type (i.e. when doing a test for each gene in genomic studies).

Submitted a proposed patch that should solve the issue by producing an error
"data is essentially constant"
- which is the same error message found in t-test under similar conditions.

P.S. First time writing to this list. Read all the guides of posting, but sorry
in advance if I still missed any rules.

---
Karolis Koncevi?ius

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