one-of reports one randomly selected member from a provided agentset or list. For example, if we were creating a forest fire model in which a fire broke out at a random patch, we would write the following code:

create-trees 100 [
    set shape "tree"
    set color green
    move-to one-of patches
]
ask one-of trees [
    set color red
]

Things to keep in mind when using one-of:

• We can also use one-of with lists. For example, if we wanted each of our turtles to pick a random color from a predetermined list, we can write the following code: ask turtles [set color one-of [red green blue yellow]].

• If one-of is used on an empty agentset or list, NetLogo will show an error and your model will not work.

In the model example below, we have a small population of blue turtles representing healthy people. We use one-of to turn one randomly picked turtle red, which indicates an infected agent (i.e., patient zero).