Using group_by with difftime

Question

I\'ve created a dataframe with data :

idCol <- c(\'1\',\'1\',\'2\',\'2\')
stepCol <- c(\'step1\' , \'step2\' , \'step1\' , \'step2\')
timestampCol <- c         


        

Answer 1

I did some minor editing to your code but basically you need to associate the results of ymd_hms with your mydata:

mydata$diffTime <- c(0, difftime(lubridate::ymd_hms(mydata$timestamp[-1]), 
                          lubridate::ymd_hms(mydata$timestamp[-nrow(mydata)]), units="hours"))
diffTime <- mydata %>% group_by(id) %>% summarize(mean(diffTime))

Returns:

R> diffTime
# A tibble: 2 x 2
     id `mean(diffTime)`
              
1     1         0.008333
2     2         0.033333