# [Julia package for function approximation](https://github.com/JuliaApproximation/ApproxFun.jl)

using ApproxFun

x = Fun(identity, 0..100)

g = sqrt(x)

g2 = g(2)

x = Fun(identity, 0.1 .. 1.)

w = Fun(identity,0.1 .. 1.)

T = Fun(identity,0.1 .. 1.)

ν = Fun(identity,0.1 .. 1.)

#kern = ν^4 * besselj(1, 2π*√(x*x+w*w/4) )^2

kern = Fun( x -> (ν^4 * besselj(1, 2π*√(x*x+w*w/4) )^2 / (x^2 + w^2/4) - T)^2 )
