how to randomly select a neighbor patch that has a

Question

how to randomly select among all the neighbour patches that are higher instead of the highest neighbour patch? I was thinking to remove (if elevation >= [elevation] of max-one-of neighbors [elevation] [stop]) and place "[stop]" in [move-to-one-of neighbors [stop]]

to move ; a turtle procedure

if elevation >= [elevation] of max-one-of neighbors [elevation] [stop]


ifelse random-float 1 < q
[uphill elevation]
[move-to one-of neighbors]

end

Answer 1

one-of randomly selects an agent from the agentset and with creates an agentset of those agents satisfying the condition. You will also need to test that there is at least one location to go to. The selection would look like this (with threshold condition to be determined):

to move-up ; a turtle procedure
  let candidates neighbors with [elevation >= <thresholdhold condition> ]
  if any? candidates [ move-to one-of candidates]
end

If you are instead wanting to choose amongst the higher neighbours regardless of whether they are higher than some threshold, you want max-n-of. Looks like this to choose one of the 3 highest:

to move-up
  move-to one-of max-n-of 3 neighbors [elevation]
end

Answer 2

; The butterfly move procedure in turtle context
to move ; a turtle procedure
  if elevation >= [elevation] of max-one-of neighbors [elevation] [stop]
  ; Decide whether to move uphill deterministically with probability q
  ifelse random-float 1 < q
   [ uphill elevation ] ; move uphill
   [ move-to one-of neighbors ] ; otherwise move randomly
   set patches-visited patches-visited + 1
end