在 R 中，如何计算满足条件的日期之间的差异？

Question

I have two data frames ( df1 and df2 ) with start and end dates for certain events. I've determined which dates have overlapping events, defined here as having a start date in df1 that is within the start and end date of df2 . If overlap occurs then they are labeled as TRUE , if there is no overlap then they are labeled as FALSE . What I would like to know is...when Overlap is TRUE , how do I calculate the difference between start times in df2 and df1 ?

> df1$aa
    date_start  date_end    Site
1   2002-04-14  2002-04-21  aa
2   2002-06-26  2002-07-05  aa
3   2002-08-15  2002-08-20  aa
4   2004-05-12  2004-05-19  aa

> df2$bb
    date_start  date_end    Site
1   2002-04-13  2002-04-19  bb
2   2002-08-11  2002-08-19  bb
3   2005-06-09  2005-06-14  bb
4   2005-08-10  2005-08-14  bb

This code determines if there is overlap

df1$aa$Overlap <- df1$aa$date_start %in% unlist(Map(':', df2$bb$date_start, df2$bb$date_end))

> df1$aa
    date_start  date_end    Site    Overlap
1   2002-04-14  2002-04-21  aa      TRUE
2   2002-06-26  2002-07-05  aa      FALSE
3   2002-08-15  2002-08-20  aa      TRUE
4   2004-05-12  2004-05-19  aa      FALSE

You can see that there are two events (rows 1 and 3) where Overlap is TRUE . What I would like to do is determine the time difference ( Diff ) between date_start for df1 and df2 when Overlap equals TRUE .

The result I am looking for should look something like this.

    date_start  date_end    Site    Overlap   Diff
1   2002-04-13  2002-04-21  aa      TRUE      1
2   2002-08-13  2002-08-20  aa      TRUE      4

Answer 1

This should solve your problem with some nested for loops.

# Setup df1
df1 <- read.table(textConnection(
  '    date_start  date_end    Site
1   2002-04-14  2002-04-21  aa
2   2002-06-26  2002-07-05  aa
3   2002-08-15  2002-08-20  aa
4   2004-05-12  2004-05-19  aa'
))
df1$date_start <- as.Date(df1$date_start)
df1$date_end <- as.Date(df1$date_end)

# Setup df1
df2 <- read.table(textConnection(
  '    date_start  date_end    Site
1   2002-04-13  2002-04-19  bb
2   2002-08-11  2002-08-19  bb
3   2005-06-09  2005-06-14  bb
4   2005-08-10  2005-08-14  bb'
))
df2$date_start <- as.Date(df2$date_start)
df2$date_end <- as.Date(df2$date_end)


# Find overlap of dates
df1$Overlap <- df1$date_start %in% unlist(Map(':', df2$date_start, df2$date_end))


# Loop through rows
for (i in 1:nrow(df1)) {

  # Go through only those that overlap
  if (df1[i, "Overlap"]) {

    # Loop through all rows in other data frame
    for (j in 1:nrow(df2)) {

      # Check if within range of df1
      sec_date_range <- df2[j, "date_start"]:df2[j, "date_end"]
      if (df1[i, "date_start"] %in% sec_date_range) {

        # Find absolute difference in start dates
        df1[i, "diff"] <- df1[i, "date_start"] - df2[j, "date_start"]
        df1[i, "diff"] <- abs(df1[i, "diff"])
      }
    }
  }
}

# Filter and print result
df1[df1$Overlap, ]
#>   date_start   date_end Site Overlap    diff
#> 1 2002-04-14 2002-04-21   aa    TRUE  1 days
#> 3 2002-08-15 2002-08-20   aa    TRUE  4 days

^{Created on 2020-06-15 by the reprex package (v0.3.0)}