Are you kidding me?

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$ R
> unique(1,1,2,3,4)
[1] 1

This was the source of yesterday’s nasty to track down bug. What you really want is unique on a vector, as in:

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> unique(c(1,1,2,3,4))
[1] 1 2 3 4

I can’t believe someone decided to let this silently fail in the manner most likely to screw the user. Note that other functions such as sum and max behave as expected:

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> max(1,2,3,4) == max(c(1,2,3,4))
[1] TRUE
> sum(1,2,3,4) == sum(c(1,2,3,4))
[1] TRUE