Summation of complex and complex conjugate - elimination of imaginary part

Asked May 03 '18 at 15:24

Active May 03 '18 at 15:27

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When I sum a complex number and its conjugate, that have been obtained when calculating the eigenvalues of a matrix, there is still an imaginary part that is equal to zero.

ev = {-0.8957457857324409` + 3.0607525560671736` I, 
      -0.8957457857324409` - 3.0607525560671736` I};

ev[[1]] + ev[[2]]

(* Out: -1.79149 + 0. I *)

How I eliminate the imaginary part if it is zero, to have a pure real number?

Using something like Re[-1.79149 + 0. I] is not sufficient as the summation of the eigenvalues that are calculated sometime have an imaginary part.

edited May 03 '18 at 15:27

MarcoB

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asked May 03 '18 at 15:24

jarhead

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Use Chop on the result? – MarcoB May 03 '18 at 15:28
@MarcoB, that is correct! – jarhead May 03 '18 at 15:30
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I don't like Chop because it might unpack arrays (it may change the type from Complex to Real or to Integer. I would advice something like Threshold[#, 100 $MachineEpsilon] & instead. – Henrik Schumacher May 03 '18 at 15:32

Summation of complex and complex conjugate - elimination of imaginary part

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