Issue with data type in Arrays

New to Julia
1

I am new to Julia and have been recommended to post here for questions about my Julia related work.

Here is my code that attempts to create a stochastic SIR model: https://paste.ofcode.org/riNhvYWMcaxUwP9PU6wKm6 but I get the following error:

InexactError: Int64(18.45312925286407)

Stacktrace:
[1] Int64 at .\float.jl:709 [inlined]
[2] convert at .\number.jl:7 [inlined]
[3] push! at .\array.jl:868 [inlined]
[4] stochasticSIR(::Array{Float64,1}, ::Array{Float64,1}, ::Int64) at .\In[18]:33
[5] top-level scope at In[18]:51

This apparently means that a Float64 number is trying to be converted into an integer. I do not know where in my code that is done. How is this fixed and why is this happening?

1 Like
2

The stack trace points to line 33:

 push!(sirData.time, sirData.time[end] + k) # time step by k

and, indeed, you’ve initialized sirData.time to be [0] on line 17 which makes it a vector of ints. But k is a float (from the previous line).

What happens when you change that to

sirData = (dataₛ = [initialState[1]], dataᵢ = [initialState[2]], dataᵣ = [initialState[3]], time = [0.0])

?

Also, you don’t need semicolons as line / statement terminators.

Here’s a MWE:

julia> k = rand(Exponential(1/0.2))
3.1726199691536108

julia> a = [0]
1-element Array{Int64,1}:
 0

julia> push!(a, k)
ERROR: InexactError: Int64(3.1726199691536108)
...

julia> a = [0.0]
1-element Array{Float64,1}:
 0.0

julia> push!(a, k)
2-element Array{Float64,1}:
 0.0
 3.1726199691536108
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3

@anon94023334 Thank you, that fixed that issue. I actually did not realize that the “33” on line [4] meant line 33 in the stochasticSIR function. I will note that for future debugging.

I have another question, but if I need to make a thread for it please just say so.

I wrote this code to be my interpretation of Stochastic SIR model (discrete state, continuous time) in Julia - epirecipes but it is not doing what I thought it would do since when I examine each array in the sirOutput tuple they do not have matching lengths nor does the data they contain make sense. At this point the issue is a fundamental problem with how my code operates and I do not know what flaw in my architecture is. Do you?

4

Your example code is relatively small. Have you tried stepping through it with Debugger.jl to find the point where it’s execution diverges from your expectation?

5

This is getting to be more complex than I have time for, but

if randNum < (probᵢ / probₜ)
            push!(sirData.dataâ‚›, sirData.dataâ‚›[end] - 1);
            push!(sirData.dataᵢ, sirData.dataᵢ[end] + 1);
        else
            push!(sirData.dataᵢ, sirData.dataᵢ[end] - 1);
            push!(sirData.dataᵣ, sirData.dataᵣ[end] +1)
        end

pretty much guarantees that the data\_x arrays will be of different lengths: you’re pushing to data\i in both cases, but only pushing to the others conditionally.

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