將序列號轉換爲R中的字符表示

Question

我正在導入一些天氣數據，但時間戳會分散到不同的列中。我想加入這些列並從它們中創建posix對象。

datenum <- c() 
for (i in 1:dim(weather)[1]){ 

date_string <- paste0(weather$Year.UTC[i],'-',weather$Month.UTC[i],'-',weather$Day.UTC[i],'-',weather$Hour.UTC[i]) # different columns of data 
# for i = 1, date_string = "2012-12-31-23" 

datenum[i] <- as.POSIXct(date_string, format="%Y-%m-%d-%H",tz="GMT", origin = "1960-01-01") 
# for i = 1, datenum[1] = 1356994800 (numeric) 
} 

as.Date(datenum[1], origin = "1960-01-01") 
# Gives character = "7285-07-27" 

目視確認，我這樣做是正確的，我希望看到的形式;「YYYY-MM-DD HH：MM：SS」，這是我試圖獲得與作爲。日期。轉換爲序列號並返回到字符時，原點相同，但日期完全錯誤。我做錯了什麼？

Answer 1

爲什麼這麼複雜？

weather <- data.frame(Year.UTC=c(2012, 2013), 
         Month.UTC=c(1,2), 
         Day.UTC=c(1,2), 
         Hour.UTC=c(22,23)) 
weather <- within(weather, datetime <- 
       as.POSIXct(paste(Year.UTC, Month.UTC, Day.UTC, Hour.UTC, sep="-"), 
         format="%Y-%m-%d-%H", tz="UTC")) 

# Year.UTC Month.UTC Day.UTC Hour.UTC   datetime 
#1  2012   1  1  22 2012-01-01 22:00:00 
#2  2013   2  2  23 2013-02-02 23:00:00 

正如你所看到的，你根本不需要循環。