if is a primitive that allows us to define conditional agent behaviors. It has the following structure: if condition [ command(s) ]. If the given condition is true, NetLogo will run the provided code within the brackets. If the given condition is false, NetLogo will not do anything.

ask cars [
    if my-speed < 60 [
        accelerate
    ]
]

Things to keep in mind when using if:

• You can combine two or more conditional statements using and and or primitives.
• You can use the not primitive to make true statements false, and vice-versa.
• If you need your agents to follow a separate set of rules if the provided condition is false, you should use the ifelse primitive.

In the model example below, we have some patches that represent mousetraps and a few mice moving around randomly. If a mouse steps on a mousetrap, it sets its trapped? variable to true. The mice who are not trapped? continue moving around, while the ones who are trapped remain stationary.