我有一个数据集,其中包含以下信息:纬度、经度、东部标准时间。例如,对于一次观测
lat = 13
long = -2
time1 = as.POSIXlt("2014-02-12 17:00:00", tz = "EST")
我想创建一个名为timeL的新变量,表示本地时间。有什么建议可以使用R进行操作吗?
谢谢!
lat = 13
long = -2
time1 <- as.POSIXct("2014-02-12 17:00:00", tz = "EST")
# https://developers.google.com/maps/documentation/timezone/
apiurl <- sprintf("https://maps.googleapis.com/maps/api/timezone/%s?location=%s,%s×tamp=%d&sensor=%s",
"xml",
lat,
long,
as.numeric(time1),
"false")
library(XML)
tz <- xmlParse(readLines(apiurl))[["string(//time_zone_id)"]]
as.POSIXct(format(time1, tz=tz))
# [1] "2014-02-12 22:00:00 CET"
或者,根据@SymbolixAU的建议,使用他们的googleway
包:
res <- googleway::google_timezone(c(lat, long), time1, key = NULL)
as.POSIXct(format(time1, tz=res$timeZoneId))
# [1] "2014-02-12 22:00:00 CET"
library(sf)
## example data
dat = data.frame(lon = -2
, lat = 13
, time1 = as.POSIXlt("2014-02-12 17:00:00", tz = "EST"))
## convert to 'sf' object
sdf = st_as_sf(dat, coords = c("lon", "lat"), crs = 4326)
## import timezones (after extraction) and intersect with spatial points
tzs = st_read("timezones.geojson/combined.json", quiet = TRUE)
sdf = st_join(sdf, tzs)
## convert timestamps to local time
sdf$timeL = as.POSIXlt(sdf$time1, tz = as.character(sdf$tzid))
sdf$timeL
# [1] "2014-02-12 22:00:00 GMT"
st_join
而不是完整的 st_intersection
(只需在代码中替换)将时区属性连接到点上。对于这个例子来说可能不相关,但是对于更大的数据集和点与多边形查询,st_join
通常比 st_intersection
更快,并且产生相同的结果。 - TimSalabim
googleway
包中还有 API 封装器google_timezone()
,可以避免自己解析 XML。 - SymbolixAUtime1 <- as.POSIXct("2015-10-30 03:50:00", tz = "UTC")
res <- googleway::google_timezone(c(-3, 162), time1, key = NULL)
as.POSIXct(format(time1, tz=res$timeZoneId))
- Paperwing