# How to test multiple parameters with SDE?

**URL:** <https://discourse.julialang.org/t/how-to-test-multiple-parameters-with-sde/55089>\
**Category:** Numerics\
**Tags:** question\
**Created:** [February 11, 2021, 8:30pm UTC](https://discourse.julialang.org/t/how-to-test-multiple-parameters-with-sde/55089 "2021-02-11T20:30:51Z")\
**Posts on this page:** 1\
**Showing post:** 2

<div class="post-metadata">

**Author:** ![Luigi\_Marongiu](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/luigi_marongiu/32/7909_2.png) [@Luigi\_Marongiu](https://discourse.julialang.org/u/Luigi_Marongiu)\
**Post date:** [February 14, 2021, 5:03pm UTC](https://discourse.julialang.org/t/how-to-test-multiple-parameters-with-sde/55089/2 "2021-02-14T17:03:45Z")

</div>

I tried to implement the modulation manually with a for loop:

```julia
k = 1
I = [1.0, 1000.0, 10000.0, 100000.0, 1000000.0, 9000000.0, 9400000.0,
    9450000.0, 9460000.0, 9470000.0, 9480000.0, 9490000.0,
    9500000.0,  
    10000000.0, 80000000.0, 90000000.0, 100000000.0, 1000000000.0,
    10000000000.0, 100000000000.0]  
for i in I
    println(k, " > ", i)
    # inoculum
    condition1(u, t, integrator) = t==Tp
    affect1!(integrator) = integrator.u[3] += i
    cb1 = DiscreteCallback(condition1, affect1!)
    modification = CallbackSet(cb1, cb2, cb3)
    prob = ODEProblem(growth!, u0, tspan, parms)
    soln = solve(prob, AutoVern7(Rodas5()), callback=modification, tstops=[Tp])
    # plot
    clf()
    myPlot = plot(soln.t, getindex.(soln.u, 1)+getindex.(soln.u, 2),
        linestyle = "-", color = "blue")
    myPlot = plot(soln.t, getindex.(soln.u, 3),
        linestyle = "-", color = "green")
    ax = gca()
    ax.set_yscale("log")
    ax.set_xlim([1, tmax])
    ax.set_ylim([1e0, 1e10])
    legend(["Bacteria (total)", "Phages"],
        loc="lower right")
    xlabel("Time (h)")
    ylabel("Concentration (1/mL)")
    Title = string("Inoculation of ", round(i; digits = 1), " units")
    title(Title)
    fig = string("/home/gigiux/Documents/model/plot/treat/treat_", k, ".png")
    savefig(fig,
        dpi = 300, format = "png", transparent = false)
    k = k+1
end

```

and I got this breakpoint:

 ![treat](https://global.discourse-cdn.com/julialang/original/3X/b/f/bfedb07889d9cbe01f4083cb91a0da599fe040a6.png)  
So by giving more than 9 490 000 phages, the bacteria go extinct. But I could proceed to check the between 9 490 000 and 9 485 000 and so forth. This approach is a very time-consuming way of proceeding.  
Can I do the same (actually better) with SDE? Also because I would like to take into account also the time of inoculation…

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