# ERROR: Tried to remove agent with ID 66 from the space, but that agent is not on the space
**URL:** https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674
**Category:** Modelling & Simulations
**Tags:** question, modelling, agentsjl
**Created:** [November 15, 2024, 11:46am UTC](https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674 "2024-11-15T11:46:03Z")
**Posts on this page:** 8
**Page:** 1
### Author:  [@Sahil\_Khan](https://discourse.julialang.org/u/Sahil_Khan)
#### Post date: [November 15, 2024, 11:46am UTC](https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674/1 "2024-11-15T11:46:03Z")
I was wondering what is most efficient and issue free way to create random positions for agents.
At the moment Im using this where `sides = [1e3, 1e2, 5e2]`
```julia
positions = [sides .* rand(SVector{3,Float64}) for _ in 1:number_of_particles]
```
which works but sometimes throw this error when I try to run model
```julia
julia> adf, mdf = run!(model, step_point; adata = [:vel, :pos], mdata = [:count], init = true, when = (model, t) -> true, showprogress = false)
```
```julia
ERROR: Tried to remove agent with ID 66 from the space, but that agent is not on the space
Stacktrace:
[1] error(s::LazyString)
@ Base ./error.jl:35
[2] remove_agent_from_space!
@ ~/.julia/packages/Agents/dTr7O/src/spaces/continuous.jl:143 [inlined]
[3] move_agent!(agent::CELL, pos::SVector{…}, model::StandardABM{…})
@ Agents ~/.julia/packages/Agents/dTr7O/src/spaces/continuous.jl:157
[4] walk!
@ ~/.julia/packages/Agents/dTr7O/src/spaces/walk.jl:64 [inlined]
[5] move_agent!
@ ~/.julia/packages/Agents/dTr7O/src/spaces/continuous.jl:187 [inlined]
[6] agent_step!(agent::CELL, model::StandardABM{…})
@ Main ~/PhD/Program_Julia/code/abm_vs_prob_test_eqidistance.jl:211
[7] step_ahead!(model::StandardABM{…}, agent_step!::typeof(agent_step!), model_step!::typeof(model_step!), n::Int64, t::Base.RefValue{…})
@ Agents ~/.julia/packages/Agents/dTr7O/src/simulations/step_standard.jl:17
[8] step!
@ ~/.julia/packages/Agents/dTr7O/src/simulations/step_standard.jl:5 [inlined]
[9] _run!(model::StandardABM{…}, df_agent::DataFrame, df_model::DataFrame, n::Float64, when::Function, when_model::Function, mdata::Vector{…}, adata::Vector{…}, obtainer::typeof(identity), dt::Int64, p::ProgressUnknown)
@ Agents ~/.julia/packages/Agents/dTr7O/src/simulations/collect.jl:166
[10] run!(model::StandardABM{…}, n::Float64; when::Function, when_model::Function, mdata::Vector{…}, adata::Vector{…}, obtainer::Function, showprogress::Bool, init::Bool, dt::Float64)
@ Agents ~/.julia/packages/Agents/dTr7O/src/simulations/collect.jl:148
[11] top-level scope
@ ~/PhD/Program_Julia/code/abm_vs_prob_test_eqidistance.jl:269
Some type information was truncated. Use `show(err)` to see complete types.
```
Although based on position output seems agent is in space.
```julia
julia> model[66].pos
3-element SVector{3, Float64} with indices SOneTo(3):
599.9812375700334
62.84457279233983
486.74628139637053
```
---
### Author:  [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)
#### Post date: [December 11, 2024, 10:48am UTC](https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674/2 "2024-12-11T10:48:20Z")
@Sahil_Khan, I encountered the same problem. The agent is in the space, but an error is thrown. Did you figure out a solution?
---
### Author:  [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)
#### Post date: [December 11, 2024, 2:39pm UTC](https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674/3 "2024-12-11T14:39:56Z")
I tried to simplify the example. It appears to happen several cycles after reflecting off a boundary.
> **Summary**
>
> `######################################################################################################
>
> # load dependencies
>
> ######################################################################################################
> cd(@ **DIR** )
> using Pkg
> Pkg.activate(“../../..”)
> using Agents
> using CairoMakie
> using Random
> ######################################################################################################
>
> # define model
>
> ######################################################################################################
> @agent struct PoorSoul(ContinuousAgent{2, Float64})
> mass::Float64
> end
>
> function handle\_collision(agent, model)
> x, y = agent.pos
> vx, vy = agent.vel
> if x ≤ 0.0
> println(“enter 1”)
> x = 0.0
> vx \< 0.0 && (vx = -vx)
> end
> if x ≥ model.max\_bound
> println(“enter 2”)
> x = model.max\_bound
> vx \> 0.0 && (vx = -vx)
> end
> if y ≤ 0.0
> println(“enter 3”)
> y = 0.0
> vy \< 0.0 && (vy = -vy)
> end
> if y ≥ model.max\_bound
> println(“enter 4”)
> y = model.max\_bound
> vy \> 0.0 && (vy = -vy)
> end
> return SVector(x, y), SVector(vx, vy)
> end
>
> function initialize(;
> speed = .002,
> interaction\_radius = 0.012,
> dt = 1.0,
> max\_bound = 1,
> n\_agents,
> )
> properties = (;
> interaction\_radius,
> dt,
> max\_bound,
> )
> space = ContinuousSpace((1, 1); spacing = 0.02, periodic = false)
> model = StandardABM(
> PoorSoul,
> space;
> agent\_step!,
> model\_step!,
> properties
> )
>
> ```
> # Add initial individuals
> for _ ∈ 1:n_agents
> pos = Tuple(rand(Uniform(0, max_bound), 2))
> mass = 1
> vel = sincos(2π * rand(abmrng(model))) .* speed
> add_agent!(pos, model; vel, mass)
> end
> return model
>
> ```
>
> end
>
> function model\_step!(model)
> r = model.interaction\_radius
> for (a1, a2) in interacting\_pairs(model, r, :nearest)
> elastic\_collision!(a1, a2, :mass)
> end
> end
>
> function agent\_step!(agent, model)
> println(“agent id (agent.id)") new\_position, new\_velocity = handle\_collision(agent, model) println("current position (agent.pos)”)
> println(“new position $new\_position”)
> println(“”)
> agent.vel = new\_velocity
> agent.pos = new\_position
> move\_agent!(agent, model, model.dt)
> end
>
> Random.seed!(658)
> model = initialize(; n\_agents = 10, max\_bound = .40)
> run!(model, 40)
>
> # abmvideo(
>
> # “socialdist4.mp4”,
>
> # model;
>
> # title = “SIR model”,
>
> # frames = 300,
>
> # #agent\_color = sir\_colors,
>
> # agent\_size = 10,
>
> # spf = 1,
>
> # framerate = 20
>
> # )
>
> `
Here is the error several steps after reflexing off the boundary x = .40.
```julia-auto
agent id 1
current position [0.39891378941222266, 0.22174779298576894]
new position [0.39891378941222266, 0.22174779298576894]
ERROR: Tried to remove agent with ID 1 from the space, but that agent is not on the space
Stacktrace:
```
---
### Author:  [@Sahil\_Khan](https://discourse.julialang.org/u/Sahil_Khan)
#### Post date: [December 11, 2024, 3:26pm UTC](https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674/4 "2024-12-11T15:26:50Z")
> [@Christopher\_Fisher](#):
>
> handle\_collision(agent, model)
Hello, 🙂
Solution to problem is : `move_agent!(agent, new_position, model) `
Use above line in `agent_step()` before moving the agent.
Check out this code:
```julia
@agent struct PoorSoul(ContinuousAgent{2, Float64})
mass::Float64
end
function handle_collision(agent, model)
x, y = agent.pos
vx, vy = agent.vel
if x ≤ 0.0
x = 0.0
vx < 0.0 && (vx = -vx)
end
if x ≥ model.max_bound
x = model.max_bound
vx > 0.0 && (vx = -vx)
end
if y ≤ 0.0
y = 0.0
vy < 0.0 && (vy = -vy)
end
if y ≥ model.max_bound
y = model.max_bound
vy > 0.0 && (vy = -vy)
end
return @SVector([x, y]), @SVector([vx, vy])
end
function initialize(;
speed = .002,
interaction_radius = 0.012,
dt = 1.0,
max_bound = 1,
n_agents,
)
properties = (;
interaction_radius,
dt,
max_bound,
)
space = ContinuousSpace((1, 1); spacing = 0.02, periodic = false)
model = StandardABM(
PoorSoul,
space;
agent_step!,
model_step!,
properties
)
# Add initial individuals
for _ ∈ 1:n_agents
pos = Tuple(rand(Uniform(0, max_bound), 2))
mass = 1
vel = sincos(2π * rand(abmrng(model))) .* speed
add_agent!(pos, model; vel, mass)
end
return model
end
function model_step!(model)
r = model.interaction_radius
for (a1, a2) in interacting_pairs(model, r, :nearest)
elastic_collision!(a1, a2, :mass)
end
end
function agent_step!(agent, model)
new_position, new_velocity = handle_collision(agent, model)
agent.vel = new_velocity
# this move_agent function changes agent to new position
# Before you were giving new value to position but agent position was not
#actually getting updated.
move_agent!(agent, new_position, model)
move_agent!(agent, model, model.dt)
end
Random.seed!(658)
model = initialize(; n_agents = 10, max_bound = .40)
run!(model, 40)
abmvideo(
“socialdist4.mp4”,
model;
title = “SIR model”,
frames = 300,
#agent_color = sir_colors,
agent_size = 10,
spf = 1,
framerate = 20
)
```
---
### Author:  [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)
#### Post date: [December 11, 2024, 4:51pm UTC](https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674/5 "2024-12-11T16:51:24Z")
> [@Sahil\_Khan](#):
>
> `move_agent!(agent, new_position, model)`
Thank you for your help!
If I understand correctly, the critical change was the addition of `move_agent!(agent, new_position, model)` in `agent_step!`. I am assuming that it is needed to correctly set the position from the collision handler. Is that the case?
---
### Author:  [@Sahil\_Khan](https://discourse.julialang.org/u/Sahil_Khan)
#### Post date: [December 11, 2024, 5:01pm UTC](https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674/6 "2024-12-11T17:01:22Z")
Yes. Thats correct.
---
### Author:  [@Christopher\_Fisher](https://discourse.julialang.org/u/Christopher_Fisher)
#### Post date: [December 11, 2024, 5:05pm UTC](https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674/7 "2024-12-11T17:05:45Z")
Awesome. For future reference I will mark this as the solution, which is to add `move_agent!(agent, new_position, model)` when an agents position is changed. Credit goes to @Sahil_Khan for finding the solution.
**Edit** I cannot mark as the solution. Can you please mark it @Sahil_Khan ?
---
### Author:  [@Sahil\_Khan](https://discourse.julialang.org/u/Sahil_Khan)
#### Post date: [December 11, 2024, 5:12pm UTC](https://discourse.julialang.org/t/error-tried-to-remove-agent-with-id-66-from-the-space-but-that-agent-is-not-on-the-space/122674/8 "2024-12-11T17:12:25Z")
I have edited my answer to clearly state the main solution. 🙂