Exploring practical possibilities of approximating functions with frames rather than with a basis

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# JuliaApproximation/FrameFun.jl

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# FrameFun

Exploring practical possibilities of approximating functions with frames rather than with a basis. The package is heavily inspired by the Chebfun project and the Julia package ApproxFun.

using BasisFunctions, Plots, DomainSets, FrameFun
gr();

# Frame Approximations in 1D

After choosing a suitable Basis and Domain, any function can be approximated in the resulting frame:

B = Fourier(61)  -1..1
D = -0.5..0.5
f = x->x
F = Fun(f,B,D)

P = plot(F,layout = 2)
plot!(F,f,subplot=2)

The bases support any AbstractFloat subtype, so high precision approximations are straightforward:

B = Fourier(61)  big(-1)..big(1)
F = Fun(f,B,D)

P = plot(F,layout=2)
plot!(F,f,subplot=2)

# Frame Approximations in 2D

In higher dimensions, a basis can be any tensorproduct of (scaled) lower dimensional bases:

using StaticArrays
C = Disk(1.0)\Disk(0.3,SVector(0.2, 0.5))
B = (Fourier(31)  -1.3..1.3)^2
f = (x,y)->exp(x+y)
F = Fun(f,B,C)

P = heatmap(F,layout=2,aspect_ratio=1)
plot!(F,f,subplot=2,aspect_ratio=1)

Even fractal domains are not a problem:

B = (Fourier(31)  -1.0..0.35)  (Fourier(31)  -0.65..0.65)
f = (x,y)->cos(10*x*y)
F = Fun(f, B, mandelbrot())

P = heatmap(F,layout=2,aspect_ratio=1)
plot!(F,f,aspect_ratio=1,subplot=2)

## Installation

From the Julia REPL, type ] to enter Pkg mode and run

Exploring practical possibilities of approximating functions with frames rather than with a basis

v0.5.6 Latest
Apr 29, 2024

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