Re: vector multiplication

• To: mathgroup at smc.vnet.net
• Subject: [mg26182] Re: vector multiplication
• From: dkeith at sarif.com
• Date: Thu, 30 Nov 2000 01:04:21 -0500 (EST)
• References: <8rjjdh\$ofq@smc.vnet.net> <wTQD5.96470\$Zh6.258511@ralph.vnet.net> <%QWU5.9321\$b16.215543@ralph.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Tr[] is new in version 4. But this will work:

tr[m_] := Plus @@ Table[m[[i, i]], {i, Min[Dimensions[m]]}]

-- David

In article <%QWU5.9321\$b16.215543 at ralph.vnet.net>,
Heiko_Petermann at t-online.de (Heiko) wrote:
> Hello,
> i'm using mathematica 3.0 and tried to follow the example but it
> didn't work for me. Is the Funktion Tr[...]new in version 4 or
> selfdefined.
> 	Heiko
> On Sun, 08 Oct 2000 02:22:20 GMT, "Hans Staugaard"
> <hans.staugaard at get2net.dk> wrote:
>
> >Hello
> >
> >First I make a sample matrix:
> >
> >In[1]:=
> >v = Array[Plus, {5, 3}]
> >
> >Out[1]=
> >{{2, 3, 4}, {3, 4, 5}, {4, 5, 6}, {5, 6, 7}, {6, 7, 8}}
> >
> >Then pick out the diagonal elements:
> >
> >In[2]:=
> >Tr[Transpose[v].v, List]
> >
> >Out[2]=
> >{90, 135, 190}
> >
> >
> >Hans
> >
> ><Yannis.Paraskevopoulos at ubsw.com> wrote in message
> >news:8rjjdh\$ofq at smc.vnet.net...
> >> Hi there,
> >>
> >>
> >> Assume the v is a vector (1xk). I would like to calculate the v'v
and
> >> then take all the diagonal elements.
> >>
> >>
> >> yannis
> >>
> >>
> >>
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