Hey everyone,

I have a multivariate non-linear root-finding problem for which I would like to use NLsolve.jl. It does not seem to work, however:

```
using NLsolve
function f!(F, β)
F = mbagg(β, par) - mc.(β, par = par)
end
nlsolve(f!, rand(par.n))
```

The output that I receive is

```
julia> nlsolve(f!, rand(par.n))
Results of Nonlinear Solver Algorithm
* Algorithm: Trust-region with dogleg and autoscaling
* Starting Point: [0.6188824549955863, 0.5222000432685836, 0.6009845689936288, 0.5690479861423647, 0.9369342312698823, 0.2516124762445371, 0.362404246259066]
* Zero: [NaN, NaN, NaN, NaN, NaN, NaN, NaN]
* Inf-norm of residuals: 0.936934
* Iterations: 1
* Convergence: false
* |x - x'| < 0.0e+00: false
* |f(x)| < 1.0e-08: false
* Function Calls (f): 2
* Jacobian Calls (df/dx): 1
```

Which is not really informative about what is happening. Can someone help me and point me to the right direction?

Sorry for not being able to provide a MWE, but there is quite a bit in mbagg.

Maybe it has something to do that my function is only defined over positive values for beta. What can I do to solve such a constrained problem?

I am now trying the following:

```
f(β,par) = sum((mbagg(β, par) - mc.(β, par = par)).^2)
g(β) = f(β, par)
# Let's see if this works instead
lower = [1e-6, 1e-6, 1e-6, 1e-6, 1e-6, 1e-6, 1e-6]
upper = [Inf, Inf, Inf, Inf, Inf, Inf, Inf]
optimize(g, lower, upper, β_n)
```

But I receive the following error:

```
julia> optimize(g, lower, upper, β_n)
ERROR: MethodError: objects of type Array{Float64,1} are not callable
Use square brackets [] for indexing an Array.
Stacktrace:
[1] (::NLSolversBase.var"#fg!#8"{typeof(g),Array{Float64,1}})(::Array{Float64,1}, ::Array{Float64,1}) at C:\Users\Ilja\.julia\packages\NLSolversBase\5oIMo\src\objective_types\abstract.jl:13.jl:13
[2] value_gradient!!(::OnceDifferentiable{Float64,Array{Float64,1},Array{Float64,1}}, ::Array{Float64,1}) at C:\Users\Ilja\.julia\packages\NLSolversBase\5oIMo\src\interface.jl:82 at64,1},Array{Float64,1}}, ::Array{Float64,1}
[3] initial_state(::BFGS{InitialStatic{Float64},HagerZhang{Float64,Base.RefValue{Bool}},Nothing,Nothing,Flat}, ::Optim.Options{Float64,Nothing}, ::OnceDifferentiable{Float64,Array{Float64,1},Array{Float64,1}}, ::Array{Float64,1}) at C:\Users\Ilja\.julia\packages\Optim\TNmSw\src\multivariate\solvers\first_order\bfgs.jl:66
[4] optimize at C:\Users\Ilja\.julia\packages\Optim\TNmSw\src\multivariate\optimize\optimize.jl:33 [inlined]
[5] #optimize#92 at C:\Users\Ilja\.julia\packages\Optim\TNmSw\src\multivariate\optimize\interface.jl:136 [inlined] im.Options{Float64,Nothing}) at C:\Users\Ilja
[6] optimize(::Function, ::Array{Float64,1}, ::Array{Float64,1}, ::Array{Float64,1}, ::BFGS{InitialStatic{Float64},HagerZhang{Float64,Base.RefValue{Bool}},Nothing,Nothing,Flat}, ::Optim.Options{Float64,Nothing}) at C:\Users\Ilja\.julia\packages\Optim\TNmSw\src\multivariate\optimize\interface.jl:134 (repeats 2 times)
[7] top-level scope at REPL[55]:1
[8] include_string(::Function, ::Module, ::String, ::String) at .\loading.jl:1088
```

I do not really understand how I can fix the error.