UndefVarError: θ not defined

[stevengj]

@Irene

for k in num_obs
    chunk = filter(!isnan, vals_train_norm[1:k])
    node = neural_ode(chunk, size(y, 1))

    θ = train(
	    node, θ, chunk,
	    ADAMW(8e-3), maxiters;
	    cb = log_results(θs, losses)
    )

end

You need a global θ declaration in this loop, since the loop is in global scope. (It wouldn’t show up if you were writing your loop in a function.)

See Scope of Variables · The Julia Language

This is the infamous global-scope rule (Global variable scope rules lead to unintuitive behavior at the REPL/notebook · Issue #28789 · JuliaLang/julia · GitHub); the error message should be clearer in Julia 1.5.