I have a huge data file with time in seconds in column two which has been modified to delete all time values where the x or y coordinates (in column 3 and 4) are 0. This gives me a new data set where the time intervals are not all equal. From this data set I need to be able to find the values that have a 10 second interval and from there plot it against speed. If I had been able to use my original data set I could have found all values which are a product of 10 with no remainder but in this case it may be that I have deleted the integer values from the data set and consequently I would then end up with a 20 sec interval instead. I hope the problem is clearly explained. Does anyone have any idea how to solve this?