Unreachable States

Find or removes unreachable states using the transition model.

Usage

unreachable_states(
  model,
  horizon = Inf,
  sparse = "states",
  progress = TRUE,
  ...
)

remove_unreachable_states(model, ...)

Arguments

model

a MDP object.

horizon

only states that can be reached within the horizon are reachable.

sparse

logical; return a sparse logical vector?

progress

logical; show a progress bar?

...

further arguments are passed on.

Value

unreachable_states() returns a logical vector indicating the unreachable states.

remove_unreachable_states() returns a model with all unreachable states removed.

Details

The function unreachable_states() checks if states cannot be reached from any other state. It performs a depth-first search which can be slow. The search breaks cycles to avoid an infinite loop. The search depth can be restricted using horizon.

The function remove_unreachable_states() simplifies a model by removing unreachable states from the model description.

See also

Other MDP: MDP(), absorbing_states(), act(), action_state_helpers, available_actions(), find_reachable_states(), reachable_states(), sample_MDP(), sample_MDP.MDPSample(), start, transition_graph(), transition_matrix()

Author

Michael Hahsler

Examples

# create a Maze with an unreachable state

maze_unreach <- gw_read_maze(
    textConnection(c("XXXXXX", 
                     "XS X X",
                     "X  XXX",
                     "X   GX",
                     "XXXXXX")))
gw_plot(maze_unreach)


unreachable_states(maze_unreach)
#> [1] "s(2,5)"
unreachable_states(maze_unreach, sparse = FALSE)
#> s(2,2) s(3,2) s(4,2) s(2,3) s(3,3) s(4,3) s(4,4) s(2,5) s(4,5) 
#>  FALSE  FALSE  FALSE  FALSE  FALSE  FALSE  FALSE   TRUE  FALSE 

maze <- remove_unreachable_states(maze_unreach)
unreachable_states(maze)
#> character(0)
gw_plot(maze)