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Algebra on complex expressions: Collect

  • To: mathgroup at
  • Subject: [mg15225] Algebra on complex expressions: Collect
  • From: "Ross, Sean" <rosss at>
  • Date: Wed, 23 Dec 1998 01:04:02 -0500
  • Sender: owner-wri-mathgroup at

Does anyone know a way to have a Collect -like function work on
expressions with complex numbers?  If I have an expression with "x" in
it, I can use Collect[expr,x], but if I have an expression with "I" in
it, Collect[expr,I] does not separate the expression into a part with
and without "I" which would be equivalent to separating the expression
into real and imaginary parts given all symbols were real.

The RealOnly package does not seem to apply as it excludes imaginary
numbers alltogether.  ComplexExpand results in a ridiculous amount of
complexity and is worse than nothing for this purpose.  Expanding and
multiplying numerator and denominator separately by the complex
conjugate of the denominator is tedious to do manually and results in
the same problem of no way to neatly separate the real and imaginary
parts of a symbolic expression given that all symbols are real.


Sean Ross

Please reply to rosss at as I no longer subscribe to the

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