Multiple operations on list
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 : stephane.dray at umontreal.ca -------------------------------------------------------------------------------------------------- Web http://www.steph280.freesurf.fr/
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