Compute the spatial lag for idx-th observation using selected variable and current weights matrix
spatial_lag(gda_w, df)A Weight object
A data frame with selected variable only. E.g. guerry["Crm_prs"]
A data.frame with one column "Spatial Lag"
if (FALSE) {
library(sf)
guerry_path <- system.file("extdata", "Guerry.shp", package = "rgeoda")
guerry <- st_read(guerry_path)
queen_w <- queen_weights(guerry)
crm_lag <- spatial_lag(queen_w, guerry["Crm_prs"])
crm_lag
}