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