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time question

2 messages · Ralf B, David Winsemius

Original
Ralf B
# 
I have this script which I use to get an epoch with accuracy of 1
second (based on R's inability to calculate millisecond-accurate
timestamps -- at least I have not seen a straightforward solution :)
):

nowInSeconds <- as.numeric(Sys.time())
nowInMS <- nowInSeconds * 1000
print(nowInSeconds)
print(as.character(nowInMS))

when running this I get the following:
[1] 1289312002
[1] "1289312002093"


I wonder where the 93 milliseconds come from. Is this a random number?
A rounding error? Can somebody explain this?

Best,
Ralf
David Winsemius
#
On Nov 9, 2010, at 9:18 AM, Ralf B wrote:

            

      
      
      
    

        
From help page for Sys.time:

"Value
Sys.time returns an object of class "POSIXct" (see DateTimeClasses).  
On almost all systems it will have sub-second accuracy: on systems  
conforming to POSIX 1003.1-2001 the time will be reported in  
microsecond increments. On Windows it increments in clock ticks (1/60  
of a second) reported to millisecond accuracy."



You may be misled by the output of default formats.

            

      
      
      
    

        
David Winsemius, MD
West Hartford, CT