[R] vector of permutated products

[Dimitris Rizopoulos]

maybe something along these lines could be helpful:

x <- c(0.3, 0.1, 0.2)
###########
nx <- length(x)
perms <- as.matrix(expand.grid(lapply(1:nx, function(i) c(FALSE, 
TRUE))))
apply(perms, 1, function(ind) prod(c(x[ind], (1 - x[!ind]))))


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://www.med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm



----- Original Message ----- 
From: "Serguei Kaniovski" <kaniovsk at wifo.ac.at>
To: <r-help at stat.math.ethz.ch>
Sent: Wednesday, November 23, 2005 2:01 PM
Subject: [R] vector of permutated products


> Given an x-vector with, say, 3 elements, I would like to compute the
> following vector of permutated products
>
> (1-x1)*(1-x2)*(1-x3)
> (1-x1)*(1-x2)*x3
> (1-x1)*x2*(1-x3)
> x1*(1-x2)*(1-x3)
> (1-x1)*x2*x3
> x1*(1-x2)*x3
> x1*x2*(1-x3)
> x1*x2*x3
>
> Now, I already have the correctly sorted matrix of permutations! So, 
> the
> input looks something like:
>
> #input
> x<-c(0.3,0.1,0.2)
> Nx<-length(x)
> Ncomb<-2^Nx
> permat<-matrix(c(1,1,1,1,1,0,1,0,1,1,0,0,0,1,1,0,1,0,0,0,1,0,0,0),Ncomb,Nx)
>
> I code the rest as follows:
>
> #correct but clumsy code
> temp1<-t(matrix(rep(x,2^3),3,2^3))
> temp2<-t(matrix(rep(1-x,2^3),3,2^3))
> result<-apply(permat*temp1-(permat-1)*temp2,1,prod)
>
> But I would like to do without temp1 and temp2. To have something 
> like
>
> result<-apply(permat*x-(permat-1)*x,1,prod)
>
> My problem is that permat*x does not produce permat*temp1 due to the 
> way
> the element-by-element multiplication works in R. Can you help to
> simplify the above code?
>
> Thank you in advance,
> Serguei Kaniovski
> -- 
> ___________________________________________________________________
>
> Austrian Institute of Economic Research (WIFO)
>
> Name: Serguei Kaniovski P.O.Box 91
> Tel.: +43-1-7982601-243 Arsenal Objekt 20
> Fax:  +43-1-7989386 1103 Vienna, Austria
> Mail: Serguei.Kaniovski at wifo.ac.at
>
> http://www.wifo.ac.at/Serguei.Kaniovski
>
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