[R] Multiple operations on list

Stephane DRAY stephane.dray at umontreal.ca
Mon Sep 20 19:24:49 CEST 2004


suppose I have a list with matrices:


I want to compute for all combination of xi and xj (x1,x2 x1,x3 and x2,x3) 
a value.
This value is given for the pair x1,x2 by trace(x1%*%t(x1)%*%x2%*%t(x2)) / 

I know that product matrices t(xi)%*%xi can be obtained by:


but I do not know how to "mix" the values in aa to obtain the desired values.

Is there a way to do it without for loop ?

Thanks in advances,


Stéphane DRAY

Département des Sciences Biologiques
Université de Montréal, C.P. 6128, succursale centre-ville
Montréal, Québec H3C 3J7, Canada

Tel : (514) 343-6111 poste 1233         Fax : (514) 343-2293
E-mail : stephane.dray at umontreal.ca

Web                                          http://www.steph280.freesurf.fr/

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