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Re: Thread::tdlen: Objects of unequal length
*To*: mathgroup at smc.vnet.net
*Subject*: [mg121907] Re: Thread::tdlen: Objects of unequal length
*From*: A Retey <awnl at gmx-topmail.de>
*Date*: Thu, 6 Oct 2011 04:23:18 -0400 (EDT)
*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com
*References*: <j6h3re$76t$1@smc.vnet.net>
Am 05.10.2011 10:17, schrieb SysInv:
> This problem is driving me crazy. I'm trying to multiply matrices,
> where one is 1x4 (s) and the other is 4x4 (t) and the multiplication
> is s*t*Transpose[s]
>
> Despite this I get the error message that the objects is of unequal
> length. The matrices are:
>
> s={{x1,x2,x3,x4}}
>
> t={0.0284435,0.00395759,0.000211963,0.0357403},{0.00395759,0.0113862,-0.000199939,-0.000556137},{0.000211963,-0.000199939,0.00118147,-0.00043913},{
> 0.0357403,-0.000556137,-0.00043913,0.0649449}
>
> I must use double level in the 1 row matrix, since otherwise
> Transpose[] complains that it needs at least 2 levels. I tried
> without this as well, but I keep getting:
>
> Thread::tdlen : Objects of unequal length in
> {{x1,x2,x3,x4}}{{0.0284435,0.00395759,0.000211963,0.0357403},<<2>>,{<<10>>,<<3>>}}{{x1},{x2},{x3},{x4}}
> cannot be combined.>>
>
> . when I run s*t*Transpose[s].
>
> I've spent hours trying to figure this simple problem out, but
> without any luck. Any pointers guys? It doesn't help if I change the
> order of the transpose...
>
Times (*) is element wise multiplication, I guess you want Dot (.):
s.t.Transpose[s]
hth,
albert
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