立方根行为 R
Cubic Root Behaviour R
在 R 中，为什么
(-27)^(1/3)
return NaN
而
(27)^(1/3)
returns 3?
据我了解，(-27)^(1/3)有三种解法-3, 1.5+2.5971i, 1.5-2.5971i，(27)^(1/3)有三种解法3, -1.5+2.5971i, -1.5-2.5971i。那么，为什么 return 没有 -27 的解而只有 27 的实数？
help('^')
Users are sometimes surprised by the value returned, for example why
(-8)^(1/3) is NaN. For double inputs, R makes use of IEC 60559
arithmetic on all platforms, together with the C system function pow
for the ^ operator. The relevant standards define the result in many
corner cases. In particular, the result in the example above is
mandated by the C99 standard. On many Unix-alike systems the command
man pow gives details of the values in a large number of corner cases.
在 R 中，为什么
(-27)^(1/3)
return NaN
而
(27)^(1/3)
returns 3?
据我了解，(-27)^(1/3)有三种解法-3, 1.5+2.5971i, 1.5-2.5971i，(27)^(1/3)有三种解法3, -1.5+2.5971i, -1.5-2.5971i。那么，为什么 return 没有 -27 的解而只有 27 的实数？
help('^')
Users are sometimes surprised by the value returned, for example why (-8)^(1/3) is NaN. For double inputs, R makes use of IEC 60559 arithmetic on all platforms, together with the C system function pow for the ^ operator. The relevant standards define the result in many corner cases. In particular, the result in the example above is mandated by the C99 standard. On many Unix-alike systems the command man pow gives details of the values in a large number of corner cases.