[R] random walk on graph
Christos Hatzis
christos at silicoinsights.com
Thu Apr 27 17:44:27 CEST 2006
I did not look at your code in detail, but I see a potential problem in your
inner loop. I think you intended k to be in 2,3,...N+1. What you get from
your code is (2:N)+1 according to the operator precedence rules. You need
2:(N+1).
HTH,
-Christos
-----Original Message-----
From: r-help-bounces at stat.math.ethz.ch
[mailto:r-help-bounces at stat.math.ethz.ch] On Behalf Of Eric Blabac
Sent: Thursday, April 27, 2006 11:28 AM
To: r-help at stat.math.ethz.ch
Subject: [R] random walk on graph
Hi all,
I'm having issues coding a random walk on a fully connected, undirected
graph G with probability transition matrix P = (p_ij). Here is what I have
so far ...
for(i in 1:n){
for(m in 1:M){
x <- as.vector(matrix(rep(0,N+1),nc=N+1))
x[1] <- i
for(k in 2:N+1){
y <- as.vector(matrix(rep(0,n),nc=n))
r <- runif(1)
c <- c(0,cumsum(P[x[k-1],]))
for(j in 1:n){
y[j] <- (r >= c[j] & r < c[j+1])
}
x[k] <- which(y == 1)
}
L[i,m] <- x[N+1]
}
}
its giving me the error:
Error in "[<-"(`*tmp*`, k, value = integer(0)) :
nothing to replace with
no matter what I do I cant fix it ... any suggestions ?
Thanks
Eric Blabac
PhD Student - ASU Dept of Mathematics/Statistics
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