# Hessian on a parametric parametric spline

**URL:** <https://discourse.julialang.org/t/hessian-on-a-parametric-parametric-spline/35986>\
**Category:** General Usage\
**Tags:** question\
**Created:** [March 14, 2020, 8:15pm UTC](https://discourse.julialang.org/t/hessian-on-a-parametric-parametric-spline/35986 "2020-03-14T20:15:07Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![yakir12](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/yakir12/32/297_2.png) [@yakir12](https://discourse.julialang.org/u/yakir12)\
**Post date:** [March 14, 2020, 8:15pm UTC](https://discourse.julialang.org/t/hessian-on-a-parametric-parametric-spline/35986/1 "2020-03-14T20:15:07Z")

</div>

I’m not sure what the correct syntax is (got some `StackOverflowError`s) for getting the hessian of a [parametric spline](http://juliamath.github.io/Interpolations.jl/latest/control/#Parametric-splines-1) in `Interpolations.jl`.  
So from the docs:

```julia
using Interpolations

t = 0:.1:1
x = sin.(2π*t)
y = cos.(2π*t)
A = hcat(x,y)

itp = Interpolations.scale(interpolate(A, (BSpline(Cubic(Natural(OnGrid()))), NoInterp())), t, 1:2)

tfine = 0:.01:1
xs, ys = [itp(t,1) for t in tfine], [itp(t,2) for t in tfine]

```

How would I get the hessian for each element in, say, `tfine`?