Re: Oh why is life never easy? Need help with |vector|
- Subject: [mg2798] Re: Oh why is life never easy? Need help with |vector|
- From: wagner at bullwinkle.cs.Colorado.EDU (Dave Wagner)
- Date: Sun, 17 Dec 1995 02:08:39 -0500
- Approved: usenet@wri.com
- Distribution: local
- Newsgroups: wri.mathgroup
- Organization: University of Colorado, Boulder
In article <4ar5ut$2hq at dragonfly.wri.com>,
ULI WORTMANN <ULI12 at HOMER.geol.chemie.tu-muenchen.de> wrote:
>Hi All,
>
>I need to calculate v0 = v / |v| where v is a vector of size 3.
>However, |v|, which is a scalar, is for some reason (I don't
>understand) treated like a vector (at least VectorQ[|v|] gives
>TRUE). Obviously, it is impossible to divide two vectors of different
>length.
>
> |v| is defined as:
> absvec[u_] :=
> Module[{a},
> {a = Sqrt[(u[[1]]^2+u[[2]]^2+u[[3]]^2)]}]
The problem is that the body of your calculation is wrapped in list
braces, so the result comes back wrapped in list braces, which is
a vector of length 1.
Anyway, a much better way to calculate the magnitude of a vector is
like this:
absvec[u_] := Sqrt[Plus @@ (u^2)]
This function works on vectors of any length.
Dave Wagner
Principia Consulting
(303) 786-8371
dbwagner at princon.com
http://www.princon.com/princon