我目前正在运行一个 for 循环代码，并且在每个循环结束时，我正在测量循环的持续时间并打印一条消息，告诉用户循环花费了多长时间。
获得我正在使用的持续时间
duration <- difftime(end_time, start_time)
这就是我打印声明的方式
print(paste("Loop", i, "took", duration, "to run.")).
问题是每个循环的持续时间可能从 30 秒到 1 小时不等。将持续时间放在粘贴中只会将其转换为没有单位的数字。
例如
print(paste("Loop", i, "took", duration, "to run.")).
"Loop 5 took 10.5 to run"
我如何从 difftime() 中获取单位以获得类似：“Loop 5 运行了 10.5 分钟。”
PS：有些人可能会建议通过在 difftime() 中声明“单位”参数来标准化持续时间，但我希望用户可以轻松理解持续时间，这就是我将单位设置为默认“自动”的原因。
调用unitsfromduration以获取单位并通过子集获取数值duration：
print(paste("Loop", i, "took", round(duration[[1]], 2), units(duration), "to run."))
这是一个例子：
start_time <- Sys.time()
# few seconds later
end_time <- Sys.time()
duration <- difftime(end_time, start_time)
print(paste("Loop", 1, "took", round(duration[[1]], 2), units(duration), "to run."))
结果：
[1] "Loop 1 took 6.97 secs to run."
根据持续时间的范围，该单位将是自动的。请参阅此其他示例：
start_time <- Sys.time()
# few days later
end_time <- as.Date("2019-01-23")
duration <- difftime(end_time, start_time)
print(paste("Loop", 1, "took", round(duration[[1]], 2), units(duration), "to run."))
结果：
> print(paste("Loop", 1, "took", round(duration[[1]], 2), units(duration), "to run."))
[1] "Loop 1 took 5.9 days to run."
difftime一种方法是在使用时捕获输出capture.output
start_time <- as.POSIXct('2019-01-01 02:34:00')
end_time <- as.POSIXct('2019-01-01 03:14:00')
paste("Loop 5 took", capture.output(difftime(end_time, start_time)), "to run.")
#[1] "Loop 5 took Time difference of 40 mins to run."
现在您可以更改输出以使其有意义，例如从输出中删除“时间差”
sent <- capture.output(difftime(end_time, start_time))
paste("Loop 5 took",sub("Time difference of ","", sent) , "to run.")
#[1] "Loop 5 took 40 mins to run."
对于另一个输入
start_time <- as.POSIXct('2019-01-01 02:34:00')
end_time <- as.POSIXct('2019-01-01 02:34:50')
sent <- capture.output(difftime(end_time, start_time))
paste("Loop 5 took",sub("Time difference of ","", sent) , "to run.")
#[1] "Loop 5 took 50 secs to run."
你应该能够通过它units(duration)。