Однако!
CHANGES IN R 3.3.0
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NEW FEATURES
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D() now signals an error when given invalid input, rather than silently returning NA. (Request of John Nash.)
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https://cran.r-project.org/doc/manuals/r-devel/NEWS.html
...
NEW FEATURES
...
D() now signals an error when given invalid input, rather than silently returning NA. (Request of John Nash.)
...
https://cran.r-project.org/doc/manuals/r-devel/NEWS.html