r - 如何在 R 中使用 3x3 窗口对光栅执行焦点操作(均值)？我有纬度/经度值

Question

我有栅格和纬度/经度值，我想使用 3x3 窗口/内核对这些点执行焦点操作。我是 R 的新手。

Answer 1

这是一个工作流程，用于计算以定义的纬度/经度坐标为中心的 3x3 区域中栅格的平均值。

栅格化点并扩大生成的栅格以创建 3x3 区域

library(mmand)
library(raster)

# rasterize points based on lat/lon coordinates
z <- rasterize(pts[,2:3], r, field = pts$id)

# dilate z using a 3x3 box
kern <- shapeKernel(c(3,3), type="box")
z[,] <- dilate(as.matrix(z), kern)

plot(z)

计算每个区域中 r 值的平均值

# raster::zonal function (zonal statistics) is used 
# -Inf correspond to NA values and should not be taken into account
# you can change "mean" by the stats you would like to compute
zonal(r, z, fun = "mean")

#     zone     mean
#[1,] -Inf 5.563607
#[2,]    1 5.000000
#[3,]    2 3.444444
#[4,]    3 5.222222

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示例数据

library(raster)
set.seed(1)
# Generate raster of random values
r <- raster(crs = CRS("+proj=robin +datum=WGS84"), resolution = c(10, 10))
r[] <- round(runif(ncell(r), 1, 10))
# Generate data frame with lat/lon coordinates
pts <- data.frame(id = 1:3, lon = c(-100, 40, 120), lat = c(-45, 5, 35))

plot(r)
points(pts$lon, pts$lat, pch = 20, cex = 2)