寻求 2D 版本的 approxfun()

我正在 R 中寻找 2D 版本stats::approxfun()可以生成插值function来自 (x,y,z) 数据集的 f(x,y)。我在包裹中没有找到akima或其他地方。

我会尝试重新适应interp.surfaceR 包中的函数fields https://cran.r-project.org/web/packages/fields/index.html。重新改编自的示例?interp.surface:

加载包

library(fields)
#> Warning: package 'fields' was built under R version 4.1.2
#> Loading required package: spam
#> Warning: package 'spam' was built under R version 4.1.2
#> Loading required package: dotCall64
#> Warning: package 'dotCall64' was built under R version 4.1.2
#> Loading required package: grid
#> Spam version 2.7-0 (2021-06-25) is loaded.
#> Type 'help( Spam)' or 'demo( spam)' for a short introduction 
#> and overview of this package.
#> Help for individual functions is also obtained by adding the
#> suffix '.spam' to the function name, e.g. 'help( chol.spam)'.
#> 
#> Attaching package: 'spam'
#> The following objects are masked from 'package:base':
#> 
#>     backsolve, forwardsolve
#> Loading required package: viridis
#> Loading required package: viridisLite
#> 
#> Try help(fields) to get started.

加载数据

data(lennon)
obj <- list(x = 1:20, y = 1:20, z = lennon[201:220, 201:220])

定义逼近函数

approxfun_2d <- function(x, y) {
  interp.surface(obj, cbind(x, y))
}

Test it

set.seed(1)
approxfun_2d(x = runif(1, min = 1, max = 20), y = runif(1, min = 1, max = 20))
#> [1] 33.34148

绘制原始数据

image.plot(obj)

计算插值

x_interp <- runif(2e2, 1, 20)
y_interp <- runif(2e2, 1, 20)
z_interp <- approxfun_2d(x_interp, y_interp)

绘图近似

quilt.plot(x_interp, y_interp, z_interp)

^{Created on 2021-11-23 by the reprex package https://reprex.tidyverse.org (v2.0.1)}

这并不 100% 等于 2D 版本approxfun，但对于大多数用途来说可能已经足够了。