在R中的循环中替换矩阵中的行

Question

I am trying to write a simple Markov model in R. To generate the Markov trace I created a empty matrix with ncol=number of states, and nrow=number of cycles. I am writing a function using a loop to replace each row of the matrix with each cycle, but the loop is failing me.

Rounds<-function(cycles,TransMatrix){
  for (i in 1:nrow(MarkovTrace)){
    MarkovTrace[i+1,]<-as.vector(MarkovTrace[i,]%*%TransMatrix)
  }
}

Any thoughts on why this is? I am able to do this manually outside of the loop, though.

MarkovTrace[2,]<-as.vector(MarkovTrace[1,]%*%TransMatrix)
MarkovTrace[3,]<-as.vector(MarkovTrace[2,]%*%TransMatrix)

Many thanks!

Answer 1

You can use <<- operator to affect a variable from outer scopes. However also consider a coding style that obviates this need as it will make your code more re-usable and easier to debug.