Hi all, my first post here so bare with me please.

I’m also new to the Julia language and enjoying it very much so far.

Now to the point.

I’ve been trying LsqFit and wanted to implement a simple curve fitting model using a single shooting method. My goal is to estimate the rate constants of a chemical kinetics model. My code is the following:

```
using Optim
using LsqFit
using DifferentialEquations
function floudas_one(dz_dt, z, phi, t)
r_1 = phi[1]*z[1]
r_2 = phi[2]*z[2]
dz_dt[1] = -r_1
dz_dt[2] = r_1 - r_2
end
ode_fun = floudas_one
data = Float64[1.0 0.57353 0.328937 0.188654 0.108198 0.0620545 0.0355906 0.0204132 0.011708 0.00671499;
0.0 0.401566 0.589647 0.659731 0.666112 0.639512 0.597179 0.54867 0.499168 0.451377]
t = Float64[0.0, 0.111111, 0.222222, 0.333333, 0.444444, 0.555556, 0.666667, 0.777778, 0.888889, 1.0]
function lsq_ss_estimator(time_array, phi)
tspan = (t[1], t[end])
ini_cond = data[:,1]
oprob = ODEProblem(ode_fun, ini_cond, tspan, phi)
osol = solve(oprob, Tsit5(), saveat=t)
estimated = reduce(hcat, osol.u)
return estimated
end
p0 = [5., 5.]
fit = curve_fit(lsq_ss_estimator, t, data, p0)
```

However, I get the following error:

```
MethodError: no method matching mul!(::Array{Float64,1}, ::LinearAlgebra.Transpose{Float64,Array{Float64,2}}, ::Array{Float64,2})
Closest candidates are:
mul!(::AbstractArray, !Matched::Number, ::AbstractArray) at /buildworker/worker/package_linux64/build/usr/share/julia/stdlib/v1.1/LinearAlgebra/src/generic.jl:26
(...)
` in top-level scope at [base/none](#)
in curve_fit at [LsqFit/TBrzN/src/curve_fit.jl:87](#)
in #curve_fit#5 at [LsqFit/TBrzN/src/curve_fit.jl:89](#)
in lmfit at [LsqFit/TBrzN/src/curve_fit.jl:41](#)
in #lmfit#3 at [LsqFit/TBrzN/src/curve_fit.jl:44](#)
in lmfit at [LsqFit/TBrzN/src/curve_fit.jl:48](#)
in #lmfit#4 at [LsqFit/TBrzN/src/curve_fit.jl:48](#)
in levenberg_marquardt at [LsqFit/TBrzN/src/levenberg_marquardt.jl:36](#)
in #levenberg_marquardt#1 at [LsqFit/TBrzN/src/levenberg_marquardt.jl:107](#)
`
```

Since I’m new to Julia and LsqFit, I’m not so sure what I’m missing here.

Any help would be appreciated.

PS: I’m aware of the DiffEqParamEstim package and it does an awesome job, I just wanted to try a few things by myself and ran into this issue.