I am trying to calculate the total activity driver using GPS data. I've written a loop that is intended to calculate the difference in time between two consecutive points in a dataframe over the range of values, summing it as it goes.
However, the final output is much smaller than would be expected, in the order of seconds instead of hundreds of hours, which leads me to believe that it is only looping a few times or not summing the values correctly. My programming knowledge is mostly from Python, am I implementing this idea correctly in R or could I write it better? My data looks something like this:
DriveNo Date.and.Time Latitude Longitude
1 264 2014-02-01 12:12:05 41.91605 12.37186
2 264 2014-02-01 12:12:05 41.91605 12.37186
3 264 2014-02-01 12:12:12 41.91607 12.37221
4 264 2014-02-01 12:12:27 41.91619 12.37365
5 264 2014-02-01 12:12:42 41.91627 12.37490
6 264 2014-02-01 12:12:57 41.91669 12.37610
Is there a way I can save the result of each iteration to a list so that I could analyse where in the range of values a problem might be occurring?
datelist = taxi_264$Date.and.Time
dlstandard = as.POSIXlt(datelist)
diffsum = 0
for (i in range(1:83193))
{
diff = difftime(dlstandard[i], dlstandard[(i+1)], units = "secs")
diffsum = diffsum + diff
}
You can try :
diffsum <- as.numeric(sum(difftime(tail(dlstandard, -1),
head(dlstandard, -1), units = 'secs')))
This will give diffsum as sum of the differences in seconds.