apply non-integer power on column vector

Alfred Chua — Sat, 19 Jul 2008 19:54:02 -0400

Hi,
I am having a problem on how to solve the equation out.
Suppose i am having a column vector:-
s=[3;-5]
when i attempt to apply non-integer power of 3/5 on the
column vector, it is not able to obtain my desired result.
the desired answer suppose to be s=[1.933 ; -2.627] however
when i apply the following command s.^(3/5), it yields
s=[1.9332 ;-0.8116 + 2.4980i]. May i know what is the exact
command to be used to solve the problem.

Re: apply non-integer power on column vector

Arthur G — Sat, 19 Jul 2008 21:55:05 -0400

On Jul 19, 3:54=A0pm, "Alfred Chua" <alfred...@lycos.com> wrote:
> Hi,
> I am having a problem on how to solve the equation out.
> Suppose i am having a column vector:-
> s=3D[3;-5]
> when i attempt to apply non-integer power of 3/5 on the
> column vector, it is not able to obtain my desired result.
> the desired answer suppose to be s=3D[1.933 ; -2.627] however
> when i apply the following command s.^(3/5), it yields
> s=3D[1.9332 ;-0.8116 + 2.4980i]. May i know what is the exact
> command to be used to solve the problem.

=46rom the documentation for power:
"Note that for a negative value X and a non-integer value Y, if the
abs(Y) is less than one, the power function returns the complex roots.
To obtain the remaining real roots, use the nthroot function."

To obtain your desired result, combine "power" and "nthroot" as
follows:

>> nthroot([3;-5], 5).^3

ans =3D

1.9332
-2.6265

-Arthur

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apply non-integer power on column vector

Re: apply non-integer power on column vector