# \`InexactError\` in my Plots.jl related script
**URL:** https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170
**Category:** New to Julia
**Created:** [October 19, 2023, 9:53am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170 "2023-10-19T09:53:15Z")
**Posts on this page:** 12
**Page:** 1
### Author:  [@Alex\_Beck](https://discourse.julialang.org/u/Alex_Beck)
#### Post date: [October 19, 2023, 9:53am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/1 "2023-10-19T09:53:16Z")
Hello again, thanks for your help, I’ve made what you told me to, but now I have this:
```julia
ERROR: LoadError: InexactError: Int64(998.8002)
Stacktrace:
[1] Int64
@ ./float.jl:900 [inlined]
[2] convert
@ ./number.jl:7 [inlined]
[3] push!
@ ./array.jl:1060 [inlined]
[4] propagation_virus(taux_transmission::Float64, personnes_infectees_initiales::Int64, population_totale::Int64, duree_simulation::Int64)
@ Main ~/Documents/sujet veille technologique/Julia/propagation.jl:20
[5] top-level scope
@ ~/Documents/sujet veille technologique/Julia/propagation.jl:41
[6] include(fname::String)
@ Base.MainInclude ./client.jl:478
[7] top-level scope
@ REPL[1]:1
```
So here is the code :
```julia
using Plots
function propagation_virus(taux_transmission::Float64, personnes_infectees_initiales, population_totale, duree_simulation)
# Initialisation des tableaux pour le suivi des données
temps = 1:duree_simulation
susceptibles = [population_totale - personnes_infectees_initiales]
infectes = [personnes_infectees_initiales]
recuperes = [round(4/3)]
plots = [] # Stockage des tracés pour créer le GIF
for jour in 2:duree_simulation
# Calcul du nombre de nouvelles infections
nouvelles_infections = (susceptibles[jour - 1] * taux_transmission * infectes[jour - 1] / population_totale)
# Calcul du nombre de récupérés (hypothétiquement, après un certain temps)
recuperes_jour = [infectes[jour - 1] - nouvelles_infections]
# Mise à jour des tableaux
push!(susceptibles, susceptibles[jour - 1] - nouvelles_infections)
push!(infectes, infectes[jour - 1] + nouvelles_infections - recuperes_jour)
push!(recuperes, recuperes[jour - 1] + recuperes_jour)
# Création d'un graphique à chaque étape
p = plot(temps[1:jour], susceptibles[1:jour], label="Susceptibles")
plot!(temps[1:jour], infectes[1:jour], label="Infectés")
plot!(temps[1:jour], recuperes[1:jour], label="Récupérés", xlabel="Jours", ylabel="Nombre de personnes", legend=true)
push!(plots, p)
end
return plots
end
# Paramètres de la simulation
taux_transmission = 0.2 # Taux de transmission (0.2 signifie qu'une personne infecte 20% de la population)
personnes_infectees_initiales = 1
population_totale = 1000
duree_simulation = 100
# Exécution de la simulation
plots = propagation_virus(taux_transmission, personnes_infectees_initiales, population_totale, duree_simulation)
# Création du GIF
anim = @animate for p in plots
p
end
gif(anim, "propagation_virus.gif", fps = 5)
```
---
### Author:  [@cormullion](https://discourse.julialang.org/u/cormullion)
#### Post date: [October 19, 2023, 10:11am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/2 "2023-10-19T10:11:23Z")
> [@Alex\_Beck](#):
>
> `susceptibles = [population_totale - personnes_infectees_initiales]`
Hi there!
I think your first problem is that you create an array (vector) of Int64s:
```julia
susceptibles = [population_totale - personnes_infectees_initiales]
1-element Vector{Int64}:
999
```
but your first calculation is
```julia
susceptibles[jour - 1] - nouvelles_infections = 998.8002
```
and you can’t do this
```julia
push!(susceptibles, susceptibles[jour - 1] - nouvelles_infections)
```
because you can’t push a float into an array of Int64s.
---
### Author:  [@cormullion](https://discourse.julialang.org/u/cormullion)
#### Post date: [October 19, 2023, 10:16am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/3 "2023-10-19T10:16:16Z")
I think the other problems have to do with mixing up scalar and array values. Try
```julia
recuperes_jour = infectes[jour - 1] - nouvelles_infections
```
rather than
```julia
recuperes_jour = [infectes[jour - 1] - nouvelles_infections]
```
perhaps.
---
### Author:  [@nilshg](https://discourse.julialang.org/u/nilshg)
#### Post date: [October 19, 2023, 11:34am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/4 "2023-10-19T11:34:45Z")
Given that this is the third time I’ve said this in response to your post I promise it’s also the last:
You seem to be doing a simulation based on agents in a model, and therefore thinking in terms of integers (e.g. 100 infected individuals, 36 recovered individuals etc.)
In calculating these numbers however you inevitably end up with non-integer numbers: e.g. 25% of all infected recover each period, so the 100 in the first period become 75 in the second, but then 56.25 in the third. If you want to keep your models in terms of “whole agents” you therefore need to round your non-integer numbers.
The error you keep asking about has always been the same: `Int(3.5)` in Julia doesn’t work as `Int` is not rounding numbers; it will only create integers if the number you are passing in is exactly representable as an integer (e.g. `Int(3.0)` will work). Wherever you divide integers, or multiply by non-integer numbers (e.g. proportions) you will have to round your results by doing `round(Int, result)` to ensure you keep working with integers.
---
### Author:  [@Nathan\_Boyer](https://discourse.julialang.org/u/Nathan_Boyer)
#### Post date: [October 19, 2023, 12:54pm UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/5 "2023-10-19T12:54:03Z")
I was incorrect when I [suggested](https://discourse.julialang.org/t/problem-in-my-code/105021/2) removing the `Int` would fix the problem because Julia infers the type of the elements anyway. These array constructors both return the same type, so you cannot `push!` Floats into either. (Only an empty array constructor defaults to `Any`.)
```julia
julia> Int[1]
1-element Vector{Int64}:
1
julia> [1]
1-element Vector{Int64}:
1
```
You would either need to round your results to be integers before pushing, or make the array type such that it can store both Float and Int.
```julia
julia> v = Real[1]
1-element Vector{Real}:
1
julia> push!(v, 1.1)
2-element Vector{Real}:
1
1.1
```
(This error is totally unrelated to Plots.jl. You need to break your problem down into smaller pieces and get those working first before trying to rerun the entire script. Try setting `jour=2` and then step through the script in the REPL one line at a time to better understand the problem. You have been told what these errors mean and how to fix them. Now you need to work through your script slowly and implement those fixes as necessary.)
---
### Author:  [@Alex\_Beck](https://discourse.julialang.org/u/Alex_Beck)
#### Post date: [October 20, 2023, 9:01am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/6 "2023-10-20T09:01:43Z")
yes I understand, but my program still doesn’t work, and I don’t know julia enough to fix that probleme
---
### Author:  [@abraemer](https://discourse.julialang.org/u/abraemer)
#### Post date: [October 20, 2023, 9:12am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/7 "2023-10-20T09:12:20Z")
Just round the value you compute in line 20 (where the stacktrace points you to). So replace this line
> [@Alex\_Beck](#):
>
> ` nouvelles_infections = (susceptibles[jour - 1] * taux_transmission * infectes[jour - 1] / population_totale)`
with
```julia
nouvelles_infections = round(Int, susceptibles[jour - 1] * taux_transmission * infectes[jour - 1] / population_totale)
```
and it should work. Whether this is conceptually what you want, you need to figure out yourself.
---
### Author:  [@abraemer](https://discourse.julialang.org/u/abraemer)
#### Post date: [October 20, 2023, 9:14am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/8 "2023-10-20T09:14:54Z")
A better fix is probably to ensure your Arrays are Float64-Arrays. So replace:
```julia
susceptibles = [population_totale - personnes_infectees_initiales]
infectes = [personnes_infectees_initiales]
recuperes = [round(4/3)]
```
with
```julia
susceptibles = Float64[population_totale - personnes_infectees_initiales]
infectes = Float64[personnes_infectees_initiales]
recuperes = Float64[round(4/3)]
```
---
### Author:  [@abraemer](https://discourse.julialang.org/u/abraemer)
#### Post date: [October 20, 2023, 9:18am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/9 "2023-10-20T09:18:26Z")
And then you will get the next error from this line:
```julia
push!(infectes, infectes[jour - 1] + nouvelles_infections - recuperes_jour)
```
because you constructed `recuperes_jour` as an array
```julia
# square brackets "[" and "]" construct an Array!
recuperes_jour = [infectes[jour - 1] - nouvelles_infections]
```
So you will need remove the brackets from this line.
---
### Author:  [@Alex\_Beck](https://discourse.julialang.org/u/Alex_Beck)
#### Post date: [October 20, 2023, 9:27am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/10 "2023-10-20T09:27:17Z")
thank, but now I have this
```julia
LoadError: MethodError: no method matching -(::Float64, ::Vector{Float64})
For element-wise subtraction, use broadcasting with dot syntax: scalar .- array
Closest candidates are:
-(::Union{Float16, Float32, Float64})
@ Base float.jl:406
-(::T, ::T) where T<:Union{Float16, Float32, Float64}
@ Base float.jl:409
-(::Union{Float16, Float32, Float64}, ::BigFloat)
@ Base mpfr.jl:474
```
---
### Author:  [@nilshg](https://discourse.julialang.org/u/nilshg)
#### Post date: [October 20, 2023, 10:43am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/11 "2023-10-20T10:43:43Z")
I already explained this in my answer four days ago:
> [@Problem in my code](https://discourse.julialang.org/t/problem-in-my-code/105021/3):
>
> To be even clearer: nouvelles\_infections = Int[susceptibles[jour - 1] \* taux\_transmission \* infectes[jour - 1] / population\_totale] Here you are saying the number of new infections is given by the number of susceptible agents in the population yesterday, multiplied by a transmission rate and the share of infected in the total population. Clearly it is unlikely that this number will be an integer - the transmission rate is probably not an exact integer, and neither will the share of infected in…
You need to be careful about the distinction between a number (e.g. `4`) and a one-element vector holding a single number (`[4]`). They are not the same thing and the difference matters.
Not to unfairly prejudge you, but it seems to me you might have very limited experience with coding and Julia specifically. Instead of posting a full model here and then letting people on the forum debug it line-by-line, I think you might find it more productive to spend a bit of time learning the basics; [Think Julia: How to Think Like a Computer Scientist](https://benlauwens.github.io/ThinkJulia.jl/latest/book.html) is a good starting point for getting started both on programming and Julia, if you’re more of a video person I know many people like [https://www.youtube.com/c/juliafortalentedamateurs/about](https://www.youtube.com/c/juliafortalentedamateurs/about)
---
### Author:  [@abraemer](https://discourse.julialang.org/u/abraemer)
#### Post date: [October 20, 2023, 11:28am UTC](https://discourse.julialang.org/t/inexacterror-in-my-plots-jl-related-script/105170/12 "2023-10-20T11:28:17Z")
I am rather certain that my other answer solves this:
> [@abraemer](#):
>
> And then you will get the next error from this line:
>
> ```julia
> push!(infectes, infectes[jour - 1] + nouvelles_infections - recuperes_jour)
>
> ```
>
> because you constructed `recuperes_jour` as an array
>
> ```julia
> # square brackets "[" and "]" construct an Array!
> recuperes_jour = [infectes[jour - 1] - nouvelles_infections]
>
> ```
>
> So you will need remove the brackets from this line.