Hi! Not sure if I got your point. But if it is to compute apply a function to all pairs (x1,x2);(x1,x3);(x2,x3) where x1,x2,x3 are stored in a list you can take look at the sources of function listdist which computes an object of class dist from a list, in the package "pairseqsim" available from bioconducor, to get an idea how to do this.
/E *********** REPLY SEPARATOR *********** On 20.09.2004 at 13:24 Stephane DRAY wrote: >Hello, > >suppose I have a list with matrices: > >a=list(x1=matrix(rnorm(10),5,2),x2=matrix(rnorm(10),5,2),x3=matrix(rnorm(10),5,2)) > >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)) / >trace(x1%*%t(x1))*trace(x2%*%t(x2)) > >I know that product matrices t(xi)%*%xi can be obtained by: > >aa=lapply(a,crossprod) > >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, > >sincerely > >St�phane DRAY >-------------------------------------------------------------------------------------------------- > > >D�partement des Sciences Biologiques >Universit� de Montr�al, C.P. 6128, succursale centre-ville >Montr�al, Qu�bec H3C 3J7, Canada > >Tel : (514) 343-6111 poste 1233 Fax : (514) 343-2293 >E-mail : [EMAIL PROTECTED] >-------------------------------------------------------------------------------------------------- > > >Web >http://www.steph280.freesurf.fr/ > >______________________________________________ >[EMAIL PROTECTED] mailing list >https://stat.ethz.ch/mailman/listinfo/r-help >PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html ______________________________________________ [EMAIL PROTECTED] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
