Dear all,

I am successfully playing with

```
sol = solve(ensembleprob,SRIW1(),EnsembleThreads(),trajectories=ϕ,saveat=δt);
```

which generates a nice set of values. Among those values `sol[1,:,:];`

is a position, `sol[2,:,:];`

a velocity.

unfortunately, I need an acceleration…

how can I nicely proceed ?

thx !

Frédéric

auto-reply

here is my idea :

```
kt = sol[9,:,16]
```

60001-element Array{Float64,1}:

with \delta t = 0.01 then

```
lmnt = length(kt)
kt_t = Vector{Float64}(undef,lmnt);
for i in 1:lmnt kt_t[i] = (i-1)*δt end;
@time kt_acc = ForwardDiff.gradient(kt, kt_t)
```

MethodError: objects of type Array{Float64,1} are not callable

Use square brackets for indexing an Array.

where am I wrong ??

Thx !

Frédéric

@Frederic_Gilt, you may want to take a look at this discourse thread.

thx for the link, but `kt`

is solution of SDE (white noise forcing term) so I want to avoid interpolation then derivation.

I was hoping ForwardDiff to be able to help me on this

(re)auto-reply

`kt`

is not a function (callable I guess ?) so not suitable for ForwardDiff… my bad !

now shifting to FiniteDifferences package… but once again exemples are for functions (!)

anyone with a simple exemple of FiniteDifferences use with data only (data = kt, time = kt_t)

Thx a lot !

sadly ended with a five-point stencil scheme :

```
for i in 3:(lmnt-2)
kt_a[i] = (-kt[i+2]+8*kt[i+1]-8*kt[i-1]+kt[i-2])/(12*δt)
end;
```