# Error in Agent pos attribute Prisoner’s Dilemma Agents
**URL:** https://discourse.julialang.org/t/error-in-agent-pos-attribute-prisoner-s-dilemma-agents/57655
**Category:** General Usage
**Tags:** error
**Created:** [March 21, 2021, 2:05pm UTC](https://discourse.julialang.org/t/error-in-agent-pos-attribute-prisoner-s-dilemma-agents/57655 "2021-03-21T14:05:01Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Ola\_Megahed](https://discourse.julialang.org/u/Ola_Megahed)
#### Post date: [March 21, 2021, 2:05pm UTC](https://discourse.julialang.org/t/error-in-agent-pos-attribute-prisoner-s-dilemma-agents/57655/1 "2021-03-21T14:05:02Z")
I am trying to duplicate the demographic Prisoner’s Dilemma by Epstein. I am having a code problem related to moving the agent according to my below function. basically I canot get the attribute position.
function movement!(agent, model)
newsite = agent.pos
# find all unoccupied position within vision
neighbors = nearby\_positions(agent.pos, model, agent.Vision)
empty = collect(empty\_positions(model))
if length(empty) \> 0
newsite = rand(empty)
end
newsite != agent.pos && move\_agent!(agent, newsite, model)
agent.Age += 1
#play nearby neighbors
nearbyAgents = collect(nearby\_agents(agent, model, agent.Vision))
if length(nearbyAgents)\>0
for ne in 1:length(nearbyAgents)
if agent.Strategy==true && nearbyAgents[ne].Strategy== true
agent.Wealth+= payoff[:R]
elseif agent.Strategy == false && nearbyAgents[ne].Strategy == true
agent.Wealth+= payoff[:T]
elseif agent.Strategy == false && nearbyAgents[ne].Strategy == false
agent.Wealth+= payoff[:P]
elseif agent.Strategy == false && nearbyAgents[ne].Strategy == true
agent.Wealth+= payoff[:S]
end
end
end
end
movement!(Test, Model)
and I get this error
While this is how I define my agent
mutable struct Test \<: AbstractAgent
id::Int
pos::Dims{2}
Strategy::Bool
Wealth::Int
Age::Int
Max\_Age::Int
Vision::Int
end
And this is how I define my model:
#initializing agents
Model= ABM(Test,space,properties = properties,scheduler = random\_activation)
for ag in 1:N
add\_agent\_single!(
Model,rand(Bool),Intial\_Endowment,0,rand(max\_age\_dist[1]:max\_age\_dist[2]),
rand(vision\_dist[1]:vision\_dist[2])
)
end
---
### Author:  [@fnin](https://discourse.julialang.org/u/fnin)
#### Post date: [March 21, 2021, 3:06pm UTC](https://discourse.julialang.org/t/error-in-agent-pos-attribute-prisoner-s-dilemma-agents/57655/2 "2021-03-21T15:06:44Z")
As far as I can tell the problem is in `movement!(Test, Model) ` in the last line of this block:
> [@Ola\_Megahed](#):
>
> ```julia
> function movement!(agent, model)
> newsite = agent.pos
> # find all unoccupied position within vision
> neighbors = nearby_positions(agent.pos, model, agent.Vision)
> empty = collect(empty_positions(model))
> if length(empty) > 0
> newsite = rand(empty)
> end
> newsite != agent.pos && move_agent!(agent, newsite, model)
> agent.Age += 1
> #play nearby neighbors
> nearbyAgents = collect(nearby_agents(agent, model, agent.Vision))
> if length(nearbyAgents)>0
> for ne in 1:length(nearbyAgents)
> if agent.Strategy==true && nearbyAgents[ne].Strategy== true
> agent.Wealth+= payoff[:R]
> elseif agent.Strategy == false && nearbyAgents[ne].Strategy == true
> agent.Wealth+= payoff[:T]
> elseif agent.Strategy == false && nearbyAgents[ne].Strategy == false
> agent.Wealth+= payoff[:P]
> elseif agent.Strategy == false && nearbyAgents[ne].Strategy == true
> agent.Wealth+= payoff[:S]
> end
> end
> end
> end
> movement!(Test, Model)
>
> ```
`movement!`, your stepping function, needs an agent instance to work, but in the last liner it gets the Agent type `Test`.
---
### Author:  [@Ola\_Megahed](https://discourse.julialang.org/u/Ola_Megahed)
#### Post date: [March 22, 2021, 11:59pm UTC](https://discourse.julialang.org/t/error-in-agent-pos-attribute-prisoner-s-dilemma-agents/57655/3 "2021-03-22T23:59:18Z")
Thank you… I should have used Model[id] instead of Test.