Time formatting: how to write a While loop that operates for a whole minute?

问题

I have written the following function:

iterations_per_minute = function() {
    Sys.setenv(TZ='GMT+5')        ## This line is optional; it just sets my timezone   
    final_instant = as.numeric(format(Sys.time(), "%H.%M")) + 0.01
    counter = 0

    while(as.numeric(format(Sys.time(), "%H.%M")) < final_instant) {
      counter = counter + 1
    }

    return(counter)
}

You can infer from the code what the function does, but allow me to explain in lay words anyway: what number can you reach by counting as fast as possible during one minute starting from the number 1? Think of the computer doing exactly that same thing. The output of this function is the number that the computer reaches after counting for a whole minute.

Or at least that is how I would like this function to behave. It does work the way I have described if we pair exactly the call to the function with the beginning of a minute in the clock. However, it will count for less than a minute if we execute this function when the second hand of the clock is pointing at any other number besides twelve. How do I fix this?

Also, I figure I probably won't get the desired output if I execute the function between 23:59 and 0:00. How can this other issue be fixed?

回答1:

Seems to me like you're trying to introduce more moving parts than you need. Consider the following:

a <- Sys.time()
a
# [1] "2020-07-25 16:21:40 CDT"
a + 60
# [1] "2020-07-25 16:22:40 CDT"

So, we can just add 60 to Sys.time() without worrying about conversions or whatever else:

iterations_per_minute = function() {
    counter = 0
    end <- Sys.time() + 60
    while( Sys.time() < end )  {
        counter = counter + 1
    }
    return(counter)
}

Using this function, apparently my machine can count to 1474572 in one minute.

来源：https://stackoverflow.com/questions/63093569/time-formatting-how-to-write-a-while-loop-that-operates-for-a-whole-minute

标签

time

formatting