将R中的亚小时数据转换为小时和舍入时间

Question

I have a very big dataframe in R, containing weather data with the following format.

                 valid temp
    1 17/08/2014 00:20   14
    2 17/08/2014 00:50   14
    3 17/08/2014 01:20   13.5
    4 17/08/2014 01:50   13
    5 17/08/2014 02:20   12
    6 17/08/2014 02:50   10

I would like to convert these sub-hourly data to hourly, like the following.

                    valid tmpc
    1 2014-08-17 00:00:00   14
    2 2014-08-17 01:00:00   13.75
    3 2014-08-17 02:00:00   12.5

The class of df$valid is 'factor'. I have tried first converting them to Date through POSIXct, but it gives only NA values. I have also tried changing the system locale and still I get NAs.

Answer 1

Option 1: The lubridate solution using ceiling_date or round_date . It's not clear according to your data frame and results if what you want is to round or ceiling. For instance, in the first row you are rounding and in the third using ceiling. Anyways here the example:

library(lubridate)
df <- data.frame(i = 1, valid= "17/08/2014 01:28", temp = 14)
df$valid <- dmy_hm(df$valid)
df$valid_round <- ceiling_date(df$valid , unit="hours")

Results:

  i               valid temp         valid_round
1 1 2014-08-17 01:28:00   14 2014-08-17 02:00:00

Option 2: using the base functions. Use: df$valid <- as.POSIXct(strptime(df$valid, "%d/%m/%Y %H:%M", tz ="UTC")) and then round it.

Answer 2

We can do this in base R by converting to POSIXlt , set the minute to 0, convert it back to POSIXct and aggregate to get the mean of 'temp'

df1$valid <- strptime(df1$valid, "%d/%m/%Y %H:%M")
df1$valid$min <- 0
df1$valid <- as.POSIXct(df1$valid)
aggregate(temp~valid, df1, FUN = mean)