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rmatrixapplytransitionmarkov-chains

Creating Transition Matrices for Markov - summing to 1

I am building a transition matrix for some markov chains, so I need all rows to add up to 1.

I create a random ten-state 10 x 10 matrix with:

new_vector <- runif(10^2,0,1)

new_matrix <- matrix(new_vector,
                     ncol=10,
                     nrow=10,
                     byrow=TRUE,
                     dimnames=list(from_state=sprintf("State_No.%s", rep(1:10)),
                                   to_state=sprintf("State_No.%s", rep(1:10)))

But when I use apply() , {x/sum(x)} it still sums by columns and not by rows even if I've indicated margin=1.

I've succeeded by transposing and retransposing the matrix back again as below, but is there a quicker way? I have tried Rowsum and Rowsums but the error that this flags is that these functions operate on more than one dimension like an array, so not 1 line of x in a matrix.

  transition_matrix <- new_matrix %>%
       t() %>%
       apply(1, function(x) {x/sum(x)}) %>%
       t()
Solution

  • Any of the codes below will work

    prop.table(new_matrix, 1)

proportions(new_matrix, 1)

new_matrix / rowSums(new_matrix)

sweep(new_matrix, 1, rowSums(new_matrix), '/')

t(apply(new_matrix, 1, function(x)x/sum(x)))