### Setup FastTransforms and Plotting

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

Initializes the FastTransforms library, sets up a directory for generated figures, and configures the plotting backend. Ensure FastTransforms is installed and accessible.

```julia
using FastTransforms, LinearAlgebra, Plots
const GENFIGS = joinpath(pkgdir(FastTransforms), "docs/src/generated")
!isdir(GENFIGS) && mkdir(GENFIGS)
plotlyjs()
```

```julia
Plots.PlotlyJSBackend()
```

--------------------------------

### Spherical Harmonic Coefficients Example

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/sphere

This represents a matrix of spherical harmonic coefficients. These values are typically used as input for transformations or evaluations.

```text
0.105958   -0.834521   -0.225101   -0.515565    0.886148    0.287159    0.290046    0.0         0.0         0.0         0.0         0.0         0.0           0.0          0.0          0.0           0.0           0.0         0.0         0.0          0.0         0.0           0.0          0.0          0.0          0.0           0.0         0.0  0.0
0.530802   -0.266039   -0.0717606  -0.261012    0.448626    0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0           0.0          0.0          0.0           0.0           0.0         0.0         0.0          0.0         0.0           0.0          0.0          0.0          0.0           0.0         0.0  0.0
0.668154    0.140073    0.0377829   0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0           0.0          0.0          0.0           0.0           0.0         0.0         0.0          0.0         0.0           0.0          0.0          0.0          0.0           0.0         0.0  0.0
0.390394    0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0           0.0          0.0          0.0           0.0           0.0         0.0         0.0          0.0         0.0           0.0          0.0          0.0          0.0           0.0         0.0  0.0
0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0         0.0           0.0          0.0          0.0           0.0           0.0         0.0         0.0          0.0         0.0           0.0          0.0          0.0          0.0           0.0         0.0  0.0
```

--------------------------------

### Load FastTransforms Package

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/dev

Once the package is built from source, it can be loaded using the `using` keyword. This action may trigger pre-compilation if it hasn't been done already.

```julia
julia> using FastTransforms
[ Info: Precompiling FastTransforms [057dd010-8810-581a-b7be-e3fc3b93f78c]
```

--------------------------------

### Import FastTransforms Package

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/padua

Import the necessary FastTransforms package for numerical computations.

```julia
using FastTransforms
```

--------------------------------

### Plan FFTW Chebyshev-Fourier Analysis on Disk

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Creates an FFTW Chebyshev-Fourier analysis plan for data on the unit disk. This plan is used to analyze the function `F` on the disk.

```julia
PA = plan_disk_analysis(F)
```

--------------------------------

### Plan Disk to Chebyshev-Fourier Transform

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Precomputes a generalized Zernike-Chebyshev-Fourier plan for the given array `F`. This plan is used for transforming data on the disk to Chebyshev-Fourier coefficients.

```julia
α, β = 0, 0
P = plan_disk2cxf(F, α, β)
```

--------------------------------

### Import FastTransforms and LinearAlgebra

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/subspaceangles

Imports necessary libraries for fast transforms and linear algebra operations.

```julia
using FastTransforms, LinearAlgebra
```

--------------------------------

### FastTransforms for Triangle Calculus

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

This snippet demonstrates the use of FastTransforms library for calculus on a triangle. It involves planning a transform and then applying it to compute Ux.

```julia
Px = plan_tri2cheb(Fx, α+1, β, γ+1)
Ux = Px\(PA*Fx)
```

--------------------------------

### Precomputing an FFTW Chebyshev² analysis plan

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Creates a FastTransforms plan for FFTW Chebyshev analysis on a rectangularized disk. This is used for analyzing data on the disk using FFTW's Chebyshev transform capabilities.

```julia
PA = plan_rectdisk_analysis(F)
```

--------------------------------

### Build FastTransforms Package

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/dev

After setting the environment variable, use the `build` command in the Julia package manager to compile FastTransforms.jl from source. This process also builds dependencies like FFTW and TimeZones.

```julia
(@v1.5) pkg> build FastTransforms
   Building FFTW ──────────→ `~/.julia/packages/FFTW/ayqyZ/deps/build.log`
   Building TimeZones ─────→ `~/.julia/packages/TimeZones/K98G0/deps/build.log`
   Building FastTransforms → `~/.julia/dev/FastTransforms/deps/build.log`
```

--------------------------------

### Sample Function on Mapped Grid

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Calculates the function samples on the N x M mapped tensor product grid. It uses the previously defined x and z grid points.

```julia
F = [f(x[n], w[n]*z) for n in 1:N, z in z]
```

```julia
30×30 Matrix{Float64}:
 0.383725    0.383905   0.384264   0.384798  0.3855    0.386365  0.387383  0.388542  0.389832  0.391237  0.392744  0.394337  0.395997  0.397708  0.399451  0.401207  0.402957  0.404681  0.406361  0.407977  0.409512  0.410949  0.41227   0.413462  0.41451   0.415403  0.41613   0.416683   0.417055   0.417242
 0.353509    0.354039   0.355094   0.356664  0.358732  0.36128   0.364281  0.367707  0.371524  0.375695  0.380177  0.384927  0.389897  0.395036  0.400292  0.405609  0.41093   0.416197  0.421352  0.426336  0.431089  0.435556  0.439683  0.443417  0.446713  0.449527  0.451824  0.453573   0.454752   0.455346
 0.325652    0.32653    0.328275   0.330873  0.334296  0.338513  0.343483  0.349158  0.355488  0.362412  0.36987   0.377792  0.386108  0.394741  0.40361   0.412629  0.421708  0.43075   0.439655  0.44832   0.456637  0.464501  0.471805  0.478449  0.484336  0.489382  0.493512  0.496665   0.498793   0.499866
 0.29943     0.300665   0.303122   0.306774  0.311585  0.317506  0.324478  0.332436  0.341308  0.351018  0.361484  0.372625  0.384354  0.396582  0.409213  0.422145  0.435264  0.448446  0.461551  0.474426  0.486904  0.498809  0.50996   0.520175  0.529284  0.537127  0.54357   0.548501   0.551834   0.553515
 0.274261    0.275876   0.279088   0.283858  0.290132  0.297838  0.306895  0.317212  0.328692  0.341239  0.354758  0.36916   0.384358  0.400269  0.416811  0.43389   0.451401  0.469213  0.487163  0.505054  0.522647  0.539669  0.555819  0.570781  0.584246  0.595923  0.605564  0.612965   0.617979   0.620509
 0.249651    0.251685   0.255724   0.261714  0.269574  0.279203  0.290482  0.303282  0.31747   0.332923  0.349529  0.367198  0.385862  0.405474  0.426001  0.44741   0.469656  0.492656  0.516277  0.540305  0.564443  0.588294  0.611378  0.633149  0.653036  0.670489  0.685018  0.696234   0.703855   0.707707
```

--------------------------------

### Calculate SHA256 of Release Tarball (Julia)

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/dev

Download the tarball using curl, then use Julia's SHA.jl package to compute the SHA256 hash of the downloaded file. Remember to clean up the tarball.

```shell
shell> curl https://codeload.github.com/MikaelSlevinsky/FastTransforms/tar.gz/v0.6.2 --output FastTransforms.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  168k    0  168k    0     0   442k      0 --:--:-- --:--:-- --:--:--  443k

```

```julia
julia> using SHA

julia> open("FastTransforms.tar.gz") do f
           bytes2hex(sha256(f))
       end
"fd00befcb0c20ba962a8744a7b9139355071ee95be70420de005b7c0f6e023aa"

shell> rm -f FastTransforms.tar.gz

```

--------------------------------

### Function Samples Matrix

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/spinweighted

Displays the resulting matrix of function samples on the tensor product grid.

```julia
10×19 Matrix{ComplexF64}:
 0.628413+0.77788im   0.613246+0.789892im   0.603399+0.79744im    0.600106+0.79992im    0.603786+0.797146im   0.613972+0.789328im   0.629387+0.777092im   0.64815+0.761513im   0.668065+0.744103im   0.686931+0.726723im  0.702801+0.711386im    0.71416+0.699982im   0.720001+0.693973im    0.71983+0.694151im  0.713662+0.700491im   0.702017+0.71216im    0.685934+0.727664im  0.666955+0.745098im   0.647044+0.762452im
 0.626742+0.779227im  0.582025+0.813171im   0.552374+0.833596im   0.542362+0.840145im    0.55355+0.832816im   0.584193+0.811615im   0.629571+0.776943im   0.68294+0.730474im   0.736952+0.675945im   0.785185+0.619262im  0.823211+0.567736im   0.848825+0.528674im   0.861428+0.507879im   0.861065+0.508495im   0.84773+0.530428im   0.821392+0.570364im   0.782715+0.62238im   0.734019+0.679129im   0.679858+0.733344im
 0.690857+0.722991im  0.625071+0.780568im   0.580335+0.814378im   0.565059+0.82505im    0.582122+0.813101im   0.628309+0.777964im   0.694941+0.719066im  0.769832+0.638246im   0.840471+0.541857im   0.897514+0.440985im  0.936972+0.349406im   0.959893+0.280368im   0.969821+0.243819im   0.969549+0.244899im  0.958985+0.283457im   0.935221+0.354065im   0.894765+0.446538im  0.836798+0.547511im    0.76563+0.643282im
 0.799876+0.600166im  0.729022+0.68449im    0.678871+0.734257im   0.661444+0.749994im   0.680901+0.732375im   0.732596+0.680663im   0.804139+0.594441im  0.878702+0.477371im   0.940401+0.340068im    0.97989+0.199537im  0.997175+0.0751106im  0.999864-0.0165003im  0.997938-0.0641824im  0.998027-0.062782im  0.999923-0.0124432im  0.996684+0.0813636im  0.978303+0.207181im  0.937478+0.348046im   0.874727+0.484617im
 0.914598+0.404364im  0.858511+0.512795im   0.815749+0.578405im   0.800419+0.599441im    0.81752+0.5759im     0.861473+0.507803im   0.917769+0.397116im  0.967817+0.251653im   0.996186+0.0872572im   0.99722-0.07452im   0.977203-0.212305im   0.950621-0.310353im    0.93288-0.360187im   0.933439-0.358735im  0.952008-0.306074im   0.978656-0.205506im   0.997827-0.065887im   0.99532+0.0966353im  0.965471+0.260509im
 0.989052+0.147569im  0.963701+0.266985im   0.939852+0.341582im   0.930644+0.365927im   0.940896+0.338696im   0.965234+0.261387im   0.990188+0.13974im   0.999905-0.0137846im  0.983699-0.179822im    0.94183-0.33609im    0.88602-0.463647im   0.834409-0.551146im   0.804097-0.594498im   0.805021-0.593247im  0.836879-0.547388im   0.889222-0.457475im   0.944703-0.327927im  0.985349-0.170549im   0.999989-0.00462386im
  0.99096-0.134156im  0.999703-0.0243628im  0.998928+0.0462861im  0.997566+0.0697274im  0.999053+0.0435207im  0.999562-0.0295972im  0.989978-0.141225im  0.960887-0.276941im   0.908431-0.418034im   0.837893-0.545834im  0.762849-0.646576im   0.700449-0.713703im   0.665602-0.746307im   0.666649-0.745372im  0.703339-0.710855im    0.76689-0.641779im   0.842129-0.539276im   0.91195-0.410301im   0.963143-0.26899im
 0.919472-0.393156im  0.950297-0.311346im   0.966254-0.257589im   0.970887-0.23954im    0.965686-0.259711im   0.948995-0.315292im    0.91723-0.398357im  0.867837-0.49685im    0.802371-0.596825im   0.727938-0.685643im  0.656033-0.754733im   0.599431-0.800426im   0.568692-0.82255im    0.569608-0.821916im  0.602006-0.798492im   0.659781-0.751458im   0.732172-0.68112im   0.806377-0.591401im   0.871077-0.491147im
  0.80566-0.592379im  0.837633-0.546233im   0.856754-0.515725im   0.862863-0.505438im   0.856026-0.516933im   0.836173-0.548466im     0.8035-0.595305im  0.759389-0.650637im   0.707251-0.706962im   0.652712-0.757606im  0.602883-0.79783im    0.564968-0.825113im   0.544739-0.838606im   0.545338-0.838216im  0.566673-0.823943im   0.605429-0.795899im   0.655721-0.755004im  0.710305-0.703894im   0.762122-0.647434im
```

--------------------------------

### Sample Function on Mapped Grid

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

Samples the defined function f(x,y) on the mapped tensor product grid. The results are stored in a matrix F, representing the function values at the grid points.

```julia
F = [f(x[n+1], x[N-n]*w[m+1]) for n in 0:N-1, m in 0:M-1]
```

--------------------------------

### Sample Function on Tensor Product Grid

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/spinweighted

Samples the function F(r) = exp(i k⋅r) on the defined tensor product grid of θ and φ.

```julia
F = [exp(im*(k⋅r(θ,φ))) for θ in θ, φ in φ]
```

--------------------------------

### Precomputing a Dunkl-Xu–Chebyshev plan

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Creates a FastTransforms plan for Dunkl-Xu–Chebyshev² transformations on a given array F. This plan is used for transforming data between the disk and Chebyshev coefficients.

```julia
P = plan_rectdisk2cheb(F, β)
```

--------------------------------

### Compare Grid Transformations

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

Compares the generated x and u grids, and the w and v grids, to verify the relationship between the standard and mapped grids. This check ensures the transformation formulas are correctly applied.

```julia
((1 .+ u)./2 ≈ x) * ((1 .- u).*(1 .+ v')/4 ≈ reverse(x).*w')
```

--------------------------------

### Apply Plan and Adjoint Plan

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/subspaceangles

Applies the forward plan to the identity matrix and then the adjoint plan to compute the V^T V matrix, which is essential for calculating inner products.

```julia
VtV = parent(P*I)
lmul!(P', VtV)
```

--------------------------------

### Plotting a surface on the unit disk

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Generates a 3D surface plot of a function fff over the unit disk and saves it as an HTML file. Requires pre-defined X, Y, and F variables.

```julia
X = [x for x in x, z in z]
Y = [w*z for w in w, z in z]
scatter3d(vec(X), vec(Y), vec(0F); markersize=0.75, markercolor=:green)
surface!(X, Y, F; legend=false, xlabel="x", ylabel="y", zlabel="f")
savefig(joinpath(GENFIGS, "dunklxu.html"))
```

--------------------------------

### Sample Function on Tensor Product Grid

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/sphere

Samples a function on a tensor product grid using FastTransforms. This involves calculating a point on the grid and then using it to compute the function values.

```julia
Pnxy = FastTransforms.clenshaw!([0.0], c, A, B, C, [x⋅y], [1.0])[1]
F = [(F[n, m] - Pnxy)/(z(θ[n], φ[m])⋅y - x⋅y) for n in 1:N, m in 1:M]
```

--------------------------------

### Precompute Spin-0 Spherical Harmonic-Fourier Plan

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/spinweighted

Precomputes a plan for spin-0 spherical harmonic to Fourier transforms. This is useful for optimizing repeated transformations.

```julia
P = plan_spinsph2fourier(F, 0)
```

--------------------------------

### GramMatrix(cnm1::AbstractVector, cn::AbstractVector, X::AbstractMatrix)

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev

Construct a GramMatrix from its last two columns and the multiplication operator. The recurrence is built from XᵀW=WX and is used when the moment method is unstable.

```APIDOC
## `GramMatrix(cnm1::AbstractVector, cn::AbstractVector, X::AbstractMatrix)`

### Description
Construct a GramMatrix from its last two columns and the multiplication operator. The recurrence is built from XᵀW=WX and is used when the moment method is unstable (such as with Laguerre).

### Parameters
- **cnm1** (AbstractVector) - The second to last column of the Gram matrix.
- **cn** (AbstractVector) - The last column of the Gram matrix.
- **X** (AbstractMatrix) - Multiplication operator.
```

--------------------------------

### Set Environment Variable to Build from Source

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/dev

Set the FT_BUILD_FROM_SOURCE environment variable to "true" to trigger the build script for FastTransforms.jl. This allows developers to experiment with bleeding-edge source code.

```julia
julia> ENV["FT_BUILD_FROM_SOURCE"] = "true"
"true"
```

--------------------------------

### Initialize Chebyshev Transform

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/chebyshev

Initializes the size `n` for Chebyshev transform operations.

```julia
using FastTransforms
n = 20
```

--------------------------------

### Precompute FFTW Chebyshev² Plan on Triangle

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

Generates an FFTW Chebyshev² plan for analysis on a triangular domain. This plan is used for analyzing function representations on the triangle.

```julia
PA = plan_tri_analysis(F)
```

--------------------------------

### Construct GramMatrix with AbstractMatrix

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev

Constructs a symmetric positive-definite Gram matrix. Use when the inner product definition is available.

```julia
GramMatrix(W::AbstractMatrix, X::AbstractMatrix)
```

--------------------------------

### Create Function Approximation using Padua Coefficients

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/padua

Construct an approximation function f̃(x, y) using the computed Padua transform coefficients.

```julia
f̃ = (x,y) -> begin
    j = 1
    ret = 0.0
    for n in 0:N, k in 0:n
        ret += f̌[j]*cos((n-k)*acos(x)) * cos(k*acos(y))
        j += 1
    end
    ret
end
```

--------------------------------

### Initial guess for lambda

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/automaticdifferentiation

Sets the initial guess for the parameter lambda, which will be optimized.

```julia
λ = 1.0
```

--------------------------------

### Sample Function on Tensor Product Grid

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Samples the defined harmonic function 'f' on the mapped tensor product grid defined by the radial points 'r' and angular points 'θ'.

```julia
F = [f(r*cospi(θ), r*sinpi(θ)) for r in r, θ in θ]
```

--------------------------------

### Calculate Fx Gradient Samples

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

This code calculates the gradient samples for the Fx component over a grid defined by N and M. It uses a function `fx` and specific sampling points `x` and `w`.

```julia
Fx = [fx(x[n+1], x[N-n]*w[m+1]) for n in 0:N-1, m in 0:M-1]
```

--------------------------------

### Plotting Function on the Unit Disk

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Generates a 3D surface plot of the function `F` on the unit disk and saves it as an HTML file. Requires `X`, `Y`, and `F` to be defined.

```julia
X = [r*cospi(θ) for r in r, θ in θ]
Y = [r*sinpi(θ) for r in r, θ in θ]
scatter3d(vec(X), vec(Y), vec(0F); markersize=0.75, markercolor=:red)
surface!(X, Y, F; legend=false, xlabel="x", ylabel="y", zlabel="f")
savefig(joinpath(GENFIGS, "zernike.html"))
```

--------------------------------

### Precompute Laguerre-Laguerre Plan

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/subspaceangles

Creates a plan for transforming between Laguerre polynomial bases, including normalization for inner product calculations.

```julia
P = plan_lag2lag(Float64, N, α, β; norm2=true)
```

--------------------------------

### Calculate SHA256 of Release Tarball (Shell)

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/dev

Use curl to download the tarball and shasum to calculate its SHA256 hash on macOS. Ensure to remove the downloaded file afterwards.

```shell
shell> curl https://codeload.github.com/MikaelSlevinsky/FastTransforms/tar.gz/v0.6.2 --output FastTransforms.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  168k    0  168k    0     0   429k      0 --:--:-- --:--:-- --:--:--  429k

shell> shasum -a 256 FastTransforms.tar.gz
fd00befcb0c20ba962a8744a7b9139355071ee95be70420de005b7c0f6e023aa  FastTransforms.tar.gz

shell> rm -f FastTransforms.tar.gz

```

--------------------------------

### Verify Inverse Padua Transform

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/padua

Confirm that applying the inverse Padua transform to the coefficients recovers the function values on the grid.

```julia
ipaduatransform(f̌) ≈ f̃.(x,y)
```

--------------------------------

### Compute Legendre Polynomial Coefficients and Grid Points

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/sphere

Calculates coefficients A, B, C for Legendre polynomial evaluation, sets up a constant vector 'c', and computes the dot products of grid points 'z' with vector 'y'.

```julia
A = [(2k+1)/(k+1) for k in 0:N-1]
B = zeros(N)
C = [k/(k+1) for k in 0:N]
c = zeros(N); c[N] = 1
pts = vec([z(θ, φ)⋅y for θ in θ, φ in φ])
phi0 = ones(N*M)
F = reshape(FastTransforms.clenshaw!(zeros(N*M), c, A, B, C, pts, phi0), N, M)
```

```julia
15×29 Matrix{Float64}:
  0.264259    0.299171     0.304985    0.288068    0.261038    0.237692     0.228241    0.236528     0.259192    0.286391     0.304437    0.300462     0.26755      0.207601     0.130208    0.0483744   -0.0262845   -0.0865116   -0.129804   -0.156955   -0.170403    -0.170403    -0.158265    -0.132139   -0.0899937  -0.0308858   0.0429655   0.124641    0.202756
  0.212068    0.303332     0.129215   -0.186607   -0.387155   -0.383993    -0.338172   -0.379747    -0.392602   -0.206438     0.109443    0.299961     0.225231    -0.0101802   -0.207053   -0.258628    -0.187516    -0.070652     0.0323131   0.0988479   0.12977      0.130741     0.102005     0.0380582  -0.0627707  -0.180155   -0.256899   -0.215501   -0.0267606
 -0.115553    0.236712     0.221776   -0.251073   -0.32857     0.421619     0.986223    0.482429    -0.299585   -0.280602     0.198511    0.253762    -0.0930651   -0.258938    -0.0793421   0.160653     0.233501     0.154045     0.0336174  -0.0560314  -0.0990238   -0.100375    -0.0604041    0.0261339   0.145985    0.231751    0.1719     -0.0610864  -0.255787
 -0.18454    -0.186901     0.216999    0.207436   -0.278408   -0.36511     -0.189358   -0.35156     -0.304334    0.180746     0.238643   -0.165767    -0.202157     0.128252     0.217098   -0.00943667  -0.200512    -0.194373    -0.0821865   0.0208264   0.0732008    0.0748654    0.0260895   -0.074028   -0.188494   -0.206184   -0.027257    0.20837     0.147067
  0.233218   -0.0443128   -0.25662     0.0443223   0.302577    0.209245     0.107407    0.198264     0.305263    0.0716125   -0.25045    -0.0709297    0.228915     0.0560634   -0.209167   -0.109098     0.135993     0.209367     0.121014    0.0107106  -0.049922    -0.0518826    0.00472316   0.112882    0.206906    0.148044   -0.0921222  -0.214775    0.0327421
 -0.14959     0.176398     0.159536   -0.157586   -0.253853   -0.135785    -0.0630475  -0.127292    -0.249419   -0.174706     0.141057    0.191837    -0.130845    -0.171771     0.128955    0.181407    -0.058914    -0.206946    -0.154207   -0.0410986   0.0276329    0.029906    -0.034464    -0.146673   -0.208687   -0.0754426   0.17029     0.145612   -0.156134
```

--------------------------------

### Generate Radial Grid Points

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Creates the radial grid points 'r' for sampling the function on the unit disk. The points are distributed according to a specific formula related to Chebyshev polynomials.

```julia
r = [sinpi((N-n-0.5)/(2N)) for n in 0:N-1]
```

--------------------------------

### Plan Spin-Spherical Harmonic to Fourier Transform

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/spinweighted

Use this function to create a plan for transforming spin-weighted spherical harmonic data to Fourier space. Requires the input data and the spin value.

```julia
P = plan_spinsph2fourier(F, 1)
```

--------------------------------

### Compute Proriol-(α,β,γ) Coefficients

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

Calculates the Proriol-(α,β,γ) coefficients of a function F by applying a Proriol–Chebyshev² plan (P) and an FFTW Chebyshev² analysis plan (PA).

```julia
U = P\(PA*F)
```

--------------------------------

### Precompute spherical analysis plan

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/automaticdifferentiation

Creates a plan for Fourier analysis on the sphere using FFTW. This is used to transform data from a grid to spherical harmonic coefficients.

```julia
PA = plan_sph_analysis(Float64, N, M)
```

--------------------------------

### Plan Spin-Spherical Harmonic Analysis

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/spinweighted

Use this function to create a plan for analyzing spin-weighted spherical harmonic data. Requires the input data and the spin value.

```julia
PA = plan_spinsph_analysis(F, 1)
```

--------------------------------

### FastTransforms.stirlingseries

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev

Stirling's asymptotic series for Γ(z).

```APIDOC
## FastTransforms.stirlingseries — Function

Stirling's asymptotic series for Γ(z)\Gamma(z)Γ(z).

```

--------------------------------

### Generate Mapped W Grid Points

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

Generates the w grid points using a squared sinpi transformation, analogous to the x grid generation. These points are used in conjunction with the x grid for sampling.

```julia
w = [sinpi((2M-2m-1)/(4M))^2 for m in 0:M-1]
```

--------------------------------

### Precompute Spin-Weighted Spherical Harmonic Analysis Plan

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/spinweighted

Precomputes a plan for spin-weighted spherical harmonic analysis using FFTW on the sphere. This plan is used for transforming data from spherical coordinates to spherical harmonic coefficients.

```julia
PA = plan_spinsph_analysis(F, 0)
```

--------------------------------

### FastTransforms.half

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev

Compute a typed 0.5.

```APIDOC
## FastTransforms.half — Function

Compute a typed 0.5.

```

--------------------------------

### Set Proriol Series Parameters

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

Defines the parameters alpha, beta, and gamma for the Proriol series. These parameters influence the series expansion.

```julia
α, β, γ = 0, 0, 0
```

--------------------------------

### Integral Approximation on Unit Disk

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Approximates the integral of f(x,y)^2 over the disk using the squared norm of coefficients. The second value is a constant related to the integral.

```julia
norm(U)^2, π/(2*sqrt(2))*log1p(sqrt(2))
```

```julia
(0.9789599193439185, 0.9789599179781414)
```

--------------------------------

### Calculate Integral of P0,0^2 * sqrt(pi)

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

This code calculates the integral of P0,0^2 multiplied by the square root of pi, which should approximate pi/2 by harmonicity.

```julia
U[1, 1]*sqrt(π)
```

```julia
1.5707955409153043
```

--------------------------------

### Compute Partial Derivative with respect to y (Julia)

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

This code calculates the partial derivative with respect to y for a function represented by a Proriol series. It initializes a matrix Gy and iterates through the series coefficients to compute the derivative values.

```julia
Gy = zeros(Float64, N, M)
for m = 0:M-2
    for n = 0:N-2
        Gy[n+1, m+1] = 4*sqrt((m+1)*(m+β+γ+2))*U[n+1, m+2]
    end
end
Py = plan_tri2cheb(Fy, α, β+1, γ+1)
Uy = Py\(PA*Fy)
```

--------------------------------

### GramMatrix(W::AbstractMatrix, X::AbstractMatrix)

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev

Construct a symmetric positive-definite Gram matrix with data stored in W. Given a family of orthogonal polynomials P(x) and an inner product ⟨f,g⟩, the Gram matrix is defined by W[i,j]=⟨pi−1,pj−1⟩. It satisfies a skew-symmetric rank-2 displacement equation.

```APIDOC
## `GramMatrix(W::AbstractMatrix, X::AbstractMatrix)`

### Description
Construct a symmetric positive-definite Gram matrix with data stored in W. Given a family of orthogonal polynomials P(x) and an inner product ⟨f,g⟩, the Gram matrix is defined by W[i,j]=⟨pi−1,pj−1⟩. It satisfies a skew-symmetric rank-2 displacement equation (XᵀW−WX=GJGᵀ).

### Parameters
- **W** (AbstractMatrix) - Data for the Gram matrix.
- **X** (AbstractMatrix) - Transposed Jacobi matrix satisfying xP(x)=P(x)X.
```

--------------------------------

### Calculate Fy Gradient Samples

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/triangle

This code calculates the gradient samples for the Fy component over a grid defined by N and M. It uses a function `fy` and specific sampling points `x` and `w`.

```julia
Fy = [fy(x[n+1], x[N-n]*w[m+1]) for n in 0:N-1, m in 0:M-1]
```

--------------------------------

### Inverse Chebyshev Transform: First Kind Polynomials to Points

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/chebyshev

Performs the inverse transform from Chebyshev polynomials of the first kind back to Chebyshev points of the first kind.

```julia
ichebyshevtransform(f̌, Val(1)) ≈ exp.(p_1)
```

--------------------------------

### Construct GramMatrix with Last Two Columns and Multiplication Operator

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev

Constructs a GramMatrix using the last two columns and the multiplication operator. This is suitable for cases where the moment method is unstable, such as with Laguerre polynomials.

```julia
GramMatrix(cnm1::AbstractVector, cn::AbstractVector, X::AbstractMatrix)
```

--------------------------------

### Calculate x-grid points

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/disk

Generates the x-coordinates for the grid using the sine function. This is used for sampling on the rectangularized disk.

```julia
w = [sinpi((n+0.5)/N) for n in 0:N-1]
x = [sinpi((N-2n-1)/(2N)) for n in 0:N-1]
```

```julia
30-element Vector{Float64}:
  0.9986295347545738
  0.9876883405951378
  0.9659258262890683
  0.9335804264972017
  0.8910065241883678
  0.838670567945424
  0.7771459614569709
  0.7071067811865475
  0.6293203910498375
  0.5446390350150271
  0.45399049973954675
  0.35836794954530027
  0.25881904510252074
  0.15643446504023087
  0.052335956242943835
 -0.052335956242943835
 -0.15643446504023087
 -0.25881904510252074
 -0.35836794954530027
 -0.45399049973954675
 -0.5446390350150271
 -0.6293203910498375
 -0.7071067811865475
 -0.7771459614569709
 -0.838670567945424
 -0.8910065241883678
 -0.9335804264972017
 -0.9659258262890683
 -0.9876883405951378
 -0.9986295347545738
```

--------------------------------

### Inverse Chebyshev Transform: Second Kind Polynomials to First Kind Points

Source: https://juliaapproximation.github.io/FastTransforms.jl/dev/generated/chebyshev

Performs the inverse transform from Chebyshev polynomials of the second kind back to Chebyshev points of the first kind.

```julia
ichebyshevutransform(f̌, Val(1)) ≈ exp.(p_1)
```