（R，dplyr）如何聚合必须有条件地包含行的窗口数据？

Question

I've googled around, but have not found anything similar to this, but I'm hoping what I'm trying to do has already been done by someone else before.

1. I have a set of data with timestamps.

2. I need a running cumulative count of transactions per second - calculated as a true rolling second window. Would be nice to just truncate / round off to nearest second but that wont be enough for my use case.

#Timestamp	Current TPS
00:00:00.1	1	................................................................................................
00:00:00.2	2
00:00:00.3	3
00:00:00.4	4
00:00:00.5	5
00:00:00.6	6
00:00:00.7	7
00:00:00.8	8
00:00:00.9	9
00:00:01.0	10	....................................10 TPS here............................................................
00:00:01.1	10
00:00:01.2	10	.................................... still 10 TPS here............................................................
00:00:01.4	9	............ only 9 here, because no event at 00:00:01.3
00:00:01.5	9
00:00:01.5	10
00:00:01.8	8

Initially, I was planning to calculate a time interval difference between rows, but that doesn't solve the question of how to determine which rows should be included or excluded in the aggregate window.

This morning, I thought about mutating a new column that is just the subsecond portion of time. Then, I use that new column as a substraction on the time column, and cumsum it inside a 2nd if_else mutate that does a look-back over last X number of rows?

Does that sound reasonable? Have I overlooked some other/better approach?

Answer 1

library(dplyr)

timestamps <- c("00:00:00.1", "00:00:00.2", "00:00:00.3", "00:00:00.4", "00:00:00.5", "00:00:00.6", "00:00:00.7", "00:00:00.8", "00:00:00.9", "00:00:01.0", "00:00:01.1", "00:00:01.2", "00:00:01.4", "00:00:01.5", "00:00:01.5", "00:00:01.8") %>%
  lubridate::hms %>%     # convert to a time period in hours minutes seconds
  as.numeric  # convert that to a number of seconds

slider::slide_index_dbl(timestamps,
            timestamps,
            ~length(.x),   # = how many timestamps are in the window
            .before = .99)  # Note: using 1 here gave me an incorrect result, 
            # presumably due to floating point arithmetic errors 
            # https://en.wikipedia.org/wiki/Floating-point_error_mitigation
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