Re: How to remove the "0." from "0. + 1.41774i"

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• Subject: [mg131242] Re: How to remove the "0." from "0. + 1.41774i"
• From: Bob Hanlon <hanlonr357 at gmail.com>
• Date: Fri, 21 Jun 2013 05:57:10 -0400 (EDT)
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• References: <20130620084452.627F569EF@smc.vnet.net>

```A pure imaginary number is represented as a complex number. If it is
inexact, it will have 0. as the real part.

I//FullForm

Complex[0,1]

I//N

0. + 1.*I

To suppress display of the zero real part, the number needs to be exact
(e.g., rationals).

A={{-1.2,1.5},{-2.3,1.2}};

eigenvalues=Eigenvalues[A]//Rationalize[#,10^-16]&

{(116833629*I)/82408088,

-((116833629*I)/82408088)}

eigenvalues//FullForm

List[Complex[0,Rational[116833629,82408088]],Complex[0,Rational[-116833629,82408088]]]

eigenvalues//N

{0. + 1.4177446878757822*I,

0. - 1.4177446878757822*I}

Alternatively, use exact numbers throughout

A=Rationalize[A]

{{-(6/5), 3/2}, {-(23/10), 6/5}}

eigenvalues=Eigenvalues[A]

{(I*Sqrt[201])/10,

-((I*Sqrt[201])/10)}

eigenvalues//N

{0. + 1.4177446878757827*I,

0. - 1.4177446878757827*I}

Bob Hanlon

On Thu, Jun 20, 2013 at 4:44 AM, Mike Bayville <mike.bayville at gmail.com>wrote:

> Can anyone suggest a built-in function for removing  the "0." from "0. +
> 1.41774i"?
>
> Thanks!
>
> Mike
>
> INPUT
> A={{-1.2, 1.5}, {-2.3, 1.2}};
> Clear[eigenvalue];
> {eigenvalue[1], eigenvalue[2]} = Chop[Eigenvalues[A]]
> Chop[eigenvalue[1]]
> Chop[eigenvalue[2]]
>
> OUTPUT
> {0. + 1.41774i, 0. - 1.41774i}
> 0. + 1.41774i
> 0. - 1.41774i
>
>

```

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