impute-sp-lag.R

library(sf, quietly = TRUE)
library(spdep, quietly = TRUE)

nc <- read_sf(system.file("shape/nc.shp", package = "sf"))

# define neighbors
nb <- poly2nb(nc)

# choose variable
x <- nc$SID74

# create an isolated node
nb[[10]] <- 0L

# create a listw object
listw <- nb2listw(nb, zero.policy = TRUE)

# calculate lag with NA values
l1 <- lag.listw(listw, x)

# shortcut create KNN nbs
knn_nb <- sfdep::st_knn(nc$geometry, 3)

# second listw obj
listw_knn <- nb2listw(knn_nb)

# knn spatial lag
l2 <- lag.listw(listw_knn, x)

# impute values 
imputed <- ifelse(is.na(l1), l2, l1)