# Change initial condition by set\_state! DynamicalSystems.jl

**URL:** <https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064>\
**Category:** Modelling & Simulations\
**Created:** [October 17, 2023, 12:38pm UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064 "2023-10-17T12:38:02Z")\
**Posts on this page:** 9\
**Page:** 1

<div class="post-metadata">

**Author:** ![Sergey\_Novak](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sergey_novak/32/37716_2.png) [@Sergey\_Novak](https://discourse.julialang.org/u/Sergey_Novak)\
**Post date:** [October 17, 2023, 12:38pm UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064/1 "2023-10-17T12:38:02Z")

</div>

Hello!  
I’m trying to change the initial condition using the `set_state!` function and I integrate the system, but when I do this, I see that the initial state has not changed. Why doesn’t the initial condition change? Should I use `reinit!` ?

Thank for your helps!  
Code:

```julia
using StaticArrays, DifferentialEquations, DynamicalSystems

@inbounds function TM6_glial_ECM(var, par, t)

    g = log( 1.0 + exp( ( (par[9] + par[6] * var[5]) * var[3] * var[2] * var[1] + par[11]) / par[5] ) );
    U = par[10] + par[12] / ( 1.0 + exp( -50.0 * ( var[4] - par[25] ) ) );
    Hy = 1.0 / ( 1.0 + exp( -20.0 * ( var[2] - par[26] ) ) );
    Hecm = par[17] - (par[17] - par[18]) / (1.0 + exp( -(var[1] - par[20]) / par[19] ) );
    Hp = par[21] - (par[21] - par[22]) / (1.0 + exp( -(var[1] - par[23]) / par[24]) );

    dE = (-var[1] + par[5] * g) / par[1];
    dx = (1.0 - var[2]) / par[2] -var[3] * var[2] * var[1];
    du = (U - var[3]) / par[3] + U * (1.0 - var[3]) * var[1];
    dy = (-var[4]) / par[4] + par[13] * Hy;
    decm = -( par[7] + par[16] * var[6] ) * var[5] + par[14] * Hecm; 
    dp = -par[8] * var[6] + par[15] * Hp;

    return SVector(dE, dx, du, dy, decm, dp);
end

function TM6_glial_ECM_get_params()
    τ = 0.013; τD = 0.15; τF = 1.0; τy = 1.8;   
    α = 1.5; αecm = 0.001; αp = 0.01;
    J = 3.07; U0 = 0.3; ΔU0 = 0.305; 
    β = 0.438; βp = 0.01; βecm = 0.01;
    ecm0 = 0.0; ecm1 = 1.0; kecm = 0.15; θecm = 25.6;
    p0 = 0.0; p1 = 1.0; kp = 0.05; γp = 0.1; θp = 26.0; 
    ythr = 0.5; xthr = 0.9;
    αE = 5.0;
    I0 = -1.741;

    param = [τ, τD, τF, τy, α, αE, αecm, αp, J, U0, I0, ΔU0, β, βecm, βp, γp, ecm0, ecm1, kecm, θecm, p0, p1, θp, kp, ythr, xthr];
    return param;
end

t_tt = 3000;
tol = 1e-15;
integrator_setting = (alg = Vern9(), adaptive = true, abstol = tol, reltol = tol);

u0start = [0.9445509341100914, 0.74116702856987, 0.7361196042973006, 0.0646914552140727, 0.15145764079879162, 0.0009327645775731449];
params = TM6_glial_ECM_get_params();
ds = CoupledODEs(TM6_glial_ECM, u0start, params, diffeq = integrator_setting);

ds

set_parameter!(ds, 6, 4.2);
set_state!(ds, zeros(6));

ds

tr, _ = trajectory(ds, 500);
tr[1]

```

 ![image](https://global.discourse-cdn.com/julialang/original/3X/e/0/e015020f001f19e585812b4a2a1b29ba8c834acf.png)

---

<div class="post-metadata">

**Author:** ![Datseris](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/datseris/32/13406_2.png) [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Post date:** [October 17, 2023, 1:18pm UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064/2 "2023-10-17T13:18:27Z")

</div>

I don’t understand… The picture you paste clearly shows that the state _does_ change. First and second time you print the system show different states.

?

---

<div class="post-metadata">

**Author:** ![Sergey\_Novak](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sergey_novak/32/37716_2.png) [@Sergey\_Novak](https://discourse.julialang.org/u/Sergey_Novak)\
**Post date:** [October 17, 2023, 5:00pm UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064/3 "2023-10-17T17:00:52Z")

</div>

Yes, but when I calculate the trajectory, the first point from the trajectory is not the new state that I set

---

<div class="post-metadata">

**Author:** ![Datseris](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/datseris/32/13406_2.png) [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Post date:** [October 18, 2023, 7:29am UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064/4 "2023-10-18T07:29:29Z")

</div>

ok what’s the versions you are using.

---

<div class="post-metadata">

**Author:** ![Sergey\_Novak](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sergey_novak/32/37716_2.png) [@Sergey\_Novak](https://discourse.julialang.org/u/Sergey_Novak)\
**Post date:** [October 18, 2023, 7:43am UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064/5 "2023-10-18T07:43:19Z")

</div>

I use this version `DynamicalSystems v3.2.1`

---

<div class="post-metadata">

**Author:** ![Datseris](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/datseris/32/13406_2.png) [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Post date:** [October 18, 2023, 9:09am UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064/6 "2023-10-18T09:09:48Z")

</div>

Oh, of course, there is no bug. Have a look at the documentation of `trajectory` function: [DynamicalSystemsBase.jl · DynamicalSystemsBase.jl](https://juliadynamics.github.io/DynamicalSystemsBase.jl/stable/#DynamicalSystemsBase.trajectory)

The default state is the `initial_state(ds)`. of course, the `initial_state` does not change when setting the _current state_. you need to explicitly give a starting state as a third argument to `trajectory`.

---

<div class="post-metadata">

**Author:** ![Sergey\_Novak](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sergey_novak/32/37716_2.png) [@Sergey\_Novak](https://discourse.julialang.org/u/Sergey_Novak)\
**Post date:** [October 18, 2023, 9:14am UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064/7 "2023-10-18T09:14:51Z")

</div>

Thank you for help

---

<div class="post-metadata">

**Author:** ![Sergey\_Novak](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/sergey_novak/32/37716_2.png) [@Sergey\_Novak](https://discourse.julialang.org/u/Sergey_Novak)\
**Post date:** [October 18, 2023, 9:19am UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064/8 "2023-10-18T09:19:55Z")

</div>

Can I please ask another question here without creating a new topic?

---

<div class="post-metadata">

**Author:** ![Datseris](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/datseris/32/13406_2.png) [@Datseris](https://discourse.julialang.org/u/Datseris)\
**Post date:** [October 18, 2023, 9:43am UTC](https://discourse.julialang.org/t/change-initial-condition-by-set-state-dynamicalsystems-jl/105064/9 "2023-10-18T09:43:18Z")

</div>

better start a new topic! This one has been solved!