[Jprogramming] rounding complex numbers

[Bo Jacoby]

Hello J'ers

Even if a complex number is actually real it may display nonzero imaginary part because of round-off errors. Adding and subtracting 1e6j1e6 removes the round-off error, but is there a better or more general solution?

   UM=.%:%~_1^]%~[:+:[:*/~i. NB. Unitary Matrix generator

   rd=.]&.(1e6j1e6&+) NB. round-off cleaner

   u=.n+/ .*+n=.UM 3 NB. unit matrix                

   u NB. ugly display                
                 1 _2.78e_17j_1.11e_16  1.11e_16j_2.22e_16
_2.78e_17j1.11e_16                   1 _2.78e_17j_1.11e_16
 1.11e_16j2.22e_16  _2.78e_17j1.11e_16                   1

   rd u NB. nice display
1 0 0
0 1 0
0 0 1