netlogo: how to make turtles stop for a set number of ticks then continue

Question

I\'m trying to create a model where turtles walk randomly (but with a tendency for forward movement) until they land on a yellow coloured patch which represents a baited obj

Answer 1

To answer just the part about "Only the observer can ASK the set of all turtles", that error message happens if you do:

ask turtles [
  ask turtles [
    do-something
  ]
]

This isn't allowed in NetLogo because it's almost always accidental rather than intentional. You probably just wanted each turtle to "do-something" once; you probably didn't mean for each turtle to "do-something" for every possible pair of two turtles.

It's less obvious that you're having all turtles ask all turtles if it's split across procedures. So for example if you write:

to go
  ask turtles [ my-procedure ]
end

to my-procedure
  ask turtles [ do-something ]
end

It's still wrong for the same reason, but it isn't as easy to see that just from glancing at it.

Your code follows this latter pattern. You have:

to move-turtles
  ask turtles [
    ...
    continue
    ...
  ]
end

to continue
  ask turtles [
    rt -90
    ...
  ]
end

I don't think you want to do ask turtles in the continue procedure. Since you call the procedure inside ask turtles, it's already a turtle procedure. I'd suggest writing it as:

to continue  ;; turtle procedure
  rt -90
  ...
end

The comment reminds you that it's intended to be run by turtles. (We follow this style in all of the models in the Models Library.)