How to find the difference of time (Time taken to process a file) in R?

Question

I have Log data, it records the Start datetime and end datetime stamp.

Data from the log file look as below Preapred data in excel

Start_Date1 Start_Time1 Start_Millisecond1  Start_Date2 Start_Time2 Start_Millisecond2
29-11-2015  18:25:04    671 29-11-2015  18:40:05    275
29-11-2015  18:25:03    836 29-11-2015  18:40:04    333
10-11-2015  02:41:57    286 10-11-2015  02:51:52    690

When i load the data into R using Rstudio. The class of data looks as below.

Data Loaded and Its data type

I am using below line of code to convert date to POSIXlt.

nov$Start.Date1<-as.POSIXlt(as.character(nov$Start.Date1), format="%d-%m-%Y")

nov <-read.csv(file = '././data/Data For R Nov CBEFF log.csv',header = TRUE,na.strings = FALSE,stringsAsFactors = FALSE)

str(nov$Start.Time1)

nov$Start.Date1<-as.POSIXlt(as.character(nov$Start.Date1), format="%d-%m-%Y")

nov$Start.Time1<-as.POSIXlt(as.character(nov$Start.Time1), format="%H:%M:%S") nov$Start.Time1<-format(nov$Start.Time1, format="%H:%M:%S")

nov$Start.Date2<-as.POSIXlt(as.character(nov$Start.Date2), format="%d-%m-%Y")

nov$Start.Time2<-as.POSIXlt(as.character(nov$Start.Time2), format="%H:%M:%S") nov$Start.Time2<-format(nov$Start.Time2, format="%H:%M:%S")

**

> I want to caluclate time taken to complete that is > StartTime2-StartTime1

**

StartTime1 and StartTime2 are now in chr data type.

Answer 1

This should do the trick. If you had posted the data (reproducible example), I could check the code. This way it might have some typos in it.

nov<-read.delim("sample.csv", sep=";", dec=".")
nov$start1<-as.POSIXlt(paste(nov$Start_Date1,nov$Start_Time1 ,sep=" "), format="%d-%m-%Y %H:%M:%S")
nov$start2<-as.POSIXlt(paste(nov$Start_Date2,nov$Start_Time2 ,sep=" "), format="%d-%m-%Y %H:%M:%S")
nov$timediff<-as.numeric(difftime(nov$start2,nov$start1, unit="secs"))*1000+(nov$Start.Milisecond2-nov$Start.Milisecond1)

This gives you the time in miliseconds

EDIT Verified with sample data. The variable names have changed from "Start.Date1" to "Start_Date1"