Imaginary

is a monadic scalar function which multiplies the argument by the imaginary unit, usually denoted $$i$$ or $$j$$ in traditional mathematics. This can be seen as a mapping from a real number to a pure imaginary number (a complex number with the real part of 0). It was added to J as  together with initial support for complex numbers, and was adopted in Extended Dyalog APL using the glyph   as a monadic counterpart of Complex. In other APL implementations that support complex numbers, Circular with the left argument of  has the same functionality as Imaginary.

Examples
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Imaginary is equivalent to Complex with the default left argument of 0.

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Documentation

 * J Dictionary, NuVoc