如何按时间对spacetime::SDFDF
(具有完整时空网格的时空数据)进行子集化?
到目前为止,我尝试过:
library("maps")
library("maptools")
library("spacetime")
library("plm")
states.m <- map("state", plot = FALSE, fill = TRUE)
IDs <- sapply(strsplit(states.m$names, ":"), function(x) x[1])
states <- map2SpatialPolygons(states.m, IDs = IDs)
yrs <- 1970:1986
time <- as.POSIXct(paste(yrs, "-01-01", sep = ""), tz = "GMT")
data("Produc")
Produc.st <- STFDF(states[-8], time, Produc[order(Produc[2], Produc[1]),])
Produc.st@time[c(1,5,17)]
Produc.st[Produc.st@time[c(1,5,17)]]
但这给了我error: ncol(i) == 2 is not TRUE
.
有任何想法吗?