add Covariance methods

[markmbaum]

I added methods for Covariance types that weren't initially implemented:

• isstationary
• isisotropic
• sill
• nugget
• metricball
• Base.range
• scale

All of these methods pass the call to the underlying variogram, so I didn't add any new tests.

I did confirm that the example in the linked issue now works:

field = rand(
    GaussianCovariance() |> GaussianProcess,
    CartesianGrid(10, 10),
    :x => Float64,
)

closes JuliaEarth/GeoStats.jl#404

[juliohm]

Thanks for addressing the issue. Besides the small changes regarding internal fields, we also need basic tests for coverage purposes.

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[markmbaum]

Is there a public API for the γ field? I considered this but noticed

(cov::Covariance)(x₁, x₂) = sill(cov.γ) - cov.γ(x₁, x₂)

and followed along.

I could add a variogram(cov::Covariance) = cov.γ function.

[juliohm]

What I meant is that you accessed gamma.ball, the internal field of gamma. Em dom., 24 de mar. de 2024, 23:09, Mark Baum ***@***.***> escreveu:

…

Is there a public API for the γ field? I considered this but noticed (cov::Covariance)(x₁, x₂) = sill(cov.γ) - cov.γ(x₁, x₂) and followed along. I could add a variogram(cov::Covariance) = cov.γ function. — Reply to this email directly, view it on GitHub <#4 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAZQW3IFJCIJC5SQHH3372LYZ6BMJAVCNFSM6AAAAABFF5C7SKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDAMJXGA4DINZRHE> . You are receiving this because you commented.Message ID: ***@***.***>

[juliohm]

Thank you @markmbaum , attached a last round of review for this one.

[markmbaum]

I think it should be all set now. All tests passed locally.

[juliohm]

Thank you @markmbaum ! Releasing a patch for this now...