Hi! I am trying to optimize parameters for an ODE giving different weights to each entry of the solution `y`

inside the `L2Loss`

function. That is all `y[1]`

s should have some weights `w1`

while all `y[3]`

s should have some different weights `w3`

.

however: 1) I am uncertain on how to pass those weights using the `data_weight`

parameter and 2) I am uncertain on how to combine with `save_idx`

as I haven’t observed all the entries of `y`

. Here is a toy example:

```
using DifferentialEquations, DiffEqParamEstim, RecursiveArrayTools, BlackBoxOptim
#This is a toy example
function f(du,u,p,t)
du[1] = dx = p[1]*u[1] - u[2]
du[2] = dy = -3*u[2] + u[3]
du[3] = dz = -u[3] + u[1]
end
u0 = [1.0;1.0;1.0]
tspan = (0.0,10.0)
p = [1.5]
prob = ODEProblem(f,u0,tspan,p)
sol = solve(prob, Tsit5())
t = collect(range(0,stop=10,length=200))
randomized = VectorOfArray([(sol(t[i]) + .01randn(3)) for i in 1:length(t)])
data = convert(Array,randomized)[[1,3],:] #Keep only 1st and third for example
#Here I am uncertain on whether which way to structure the weights is correct
w1 = 0.5 #weights for u[1]
w3 = 100.0 #weights for u[3]
weights1 = [repeat([w1], size(data)[2]); repeat([w3], size(data)[2])]
weights2 = hcat(repeat([w1], size(data)[2]), repeat([w3], size(data)[2]))'
#This seems to work
loss = build_loss_objective(prob, Tsit5(), L2Loss(t,data; data_weight = weights1),
save_idxs = [1,3])
prob_bb = bboptimize(loss, SearchRange = (0.0,100.0), NumDimensions = 1)
#This ALSO seems to work however returns a different fitness
loss = build_loss_objective(prob, Tsit5(), L2Loss(t,data; data_weight = weights2),
save_idxs = [1,3])
prob_bb = bboptimize(loss, SearchRange = (0.0,100.0), NumDimensions = 1)
```