R POSIX %H:%M:%S Time Average

问题

I have a data frame of character times that I need to average by provider, but I'm not sure how to average them using just the time without the date. For the example below:

provider   time
USA       9:26:46
USDA      9:26:18
USDA      9:10:17
OIL       10:00:00
USA       6:20:56
USDA      7:19:13
OIL       11:00:00

The correct output for OIL would be the average between 10:00 and 11:00, and would look like:

provider     average
OIL          10:30

Does anyone know how to average just time without incorporating date using POSIX?

回答1:

mean works as expected. You can format the date to %H:%M:%S afterwards.

df <- read.table(text="provider   time
USA       9:26:46
USDA      9:26:18
USDA      9:10:17
OIL       10:00:00
USA       6:20:56
USDA      7:19:13
OIL       11:00:00",head=TRUE)

df$time <- as.POSIXct(df$time,format="%T",origin="1970-01-01")
format(as.POSIXct(tapply(df$time,df$provider,mean),origin="1970-01-01"),format="%H:%M:%S")

       OIL        USA       USDA 
"10:30:00" "07:53:51" "08:38:36" 

To get the providers' name :

m <- format(as.POSIXct(tapply(df$time,df$provider,mean),origin="1970-01-01"),format="%H:%M:%S")
m <- as.data.frame(m)
m$provider <- row.names(m)

来源：https://stackoverflow.com/questions/31710890/r-posix-hms-time-average