Stuck trying to modify a function

Hi,

I have the following data:

Path_Number <- 5
ID.Path <- c(1:Path_Number) # Make vector of ID's.
No_of_X <- sample(50:550, length(ID.Path), replace=TRUE) #
X <- split(sample(1:10000, sum(No_of_X), replace=TRUE), rep(ID.Path,
No_of_X))
Y <- lapply(X,function(x) sample(x, round(runif(1, min=10, max=50))))

X and Y are both lists, and I've made the following function to work
on that data as part of a simulation I'm building:

Mutate<-function(x){
  l<-0
  for(i in x){
    l2<-0
    l<-l+1
    for(i in x[[l]]){
      l2<-l2+1
      if(runif(1) < 0.9) ifelse(runif(1) <0.5, x[[l]][l2] <-
x[[l]][l2]+1, x[[l]][l2] <- x[[l]][l2]-1)
    }
  }
  return(x)
}

I call this with Effectors<-Mutate(X)
The function is designed to alter the values of each element in X by
either + or - 1 (50:50 chance wether + or -). However Y, elements of
which are a subset of the corresponding elements of X, need to be
consistent i.e. if a value in X is changed, and that value is part of
the Y subset, then the value in Y also needs to be changed. however,
since Y is a smaller subset it will not be indexed the same. My idea
was to include in the function an if statement that checks if Y
contains the value to be changed, removes it, and then after the value
in X is changed, put the new value in Y. I attempted this with:

Mutate<-function(x,y){
  l<-0
  for(i in x){
    l2<-0
    l<-l+1
    for(i in x[[l]]){
      l2<-l2+1
      if(runif(1) < 0.9){
        if(x[[l]][l2] %in% y[[l]] == TRUE){
          y[[l]]<-[which(y[[l]]!=x[[l]][l2])]

          if(runif(1) <0.5){
            x[[l]][l2] <- x[[l]][l2]+1
            y[[l]]<-append(x[[l]][l2])
          }else{
            x[[l]][l2] <- x[[l]][l2]-1
            y[[l]]<-append(x[[l]][l2])
          }
        }
        ifelse(runif(1) <0.5, x[[l]][l2] <- x[[l]][l2]+1, x[[l]][l2]
<- x[[l]][l2]-1)
      }
    }
  }
  return(list(x,y))
}

Bit of an eyesore so I've put the altered stuff in bold. I've
basically taken what the ifelse statement does in the first function,
(which is still there and run if Y does not contain the X value being
altered) and broken it down into an if and an else segment with
multiple operations in curly braces to accommodate the extra actions
needed to alter Y as well as X. This was all I could think of to keep
changes between the two "in sync", however this does not work when I
try to load the function into workspace:

Error: unexpected '}' in "}"

I hope someone can point out what it is I've done that isn't working,
or a better way to do this.

Best Wishes,

Ben W.

UEA (ENV) & The Sainsbury Laboratory.

	[[alternative HTML version deleted]]