Tommy O&#39;Dell - 1 year ago 223
R Question

# Conditional (inequality) join in data.table

I'm just trying to figure out how to do a conditional join on two data.tables.

I've written a

`sqldf`
conditional join to give me the circuits whose start or finish times are within the other's start/finish times.

``````sqldf("select dt2.start, dt2.finish, dt2.counts, dt1.id, dt1.circuit
from dt2
left join dt1 on (
(dt2.start  >= dt1.start and dt2.start  < dt1.finish) or
(dt2.finish >= dt1.start and dt2.finish < dt1.finish)
)")
``````

This gives me the correct result, but it's too slow for my large-ish data set.

What's the
`data.table`
way to do this without a vector scan?

Here's my data:

``````dt1 <- data.table(structure(list(circuit = structure(c(2L, 1L, 2L, 1L, 2L, 3L,
1L, 1L, 2L), .Label = c("a", "b", "c"), class = "factor"), start = structure(c(1393621200,
1393627920, 1393628400, 1393631520, 1393650300, 1393646400, 1393656000,
1393668000, 1393666200), class = c("POSIXct", "POSIXt"), tzone = ""),
end = structure(c(1393626600, 1393631519, 1393639200, 1393632000,
1393660500, 1393673400, 1393667999, 1393671600, 1393677000
), class = c("POSIXct", "POSIXt"), tzone = ""), id = structure(1:9, .Label = c("1001",
"1002", "1003", "1004", "1005", "1006", "1007", "1008", "1009"
), class = "factor")), .Names = c("circuit", "start", "end",
"id"), class = "data.frame", row.names = c(NA, -9L)))

dt2 <- data.table(structure(list(start = structure(c(1393621200, 1393624800, 1393626600,
1393627919, 1393628399, 1393632000, 1393639200, 1393646399, 1393650299,
1393655999, 1393660500, 1393666199, 1393671600, 1393673400), class = c("POSIXct",
"POSIXt"), tzone = ""), end = structure(c(1393624799, 1393626600,
1393627919, 1393628399, 1393632000, 1393639200, 1393646399, 1393650299,
1393655999, 1393660500, 1393666199, 1393671600, 1393673400, 1393677000
), class = c("POSIXct", "POSIXt"), tzone = ""), seconds = c(3599L,
1800L, 1319L, 480L, 3601L, 7200L, 7199L, 3900L, 5700L, 4501L,
5699L, 5401L, 1800L, 3600L), counts = c(1L, 1L, 0L, 1L, 2L, 1L,
0L, 1L, 2L, 3L, 2L, 3L, 2L, 1L)), .Names = c("start", "end",
"seconds", "counts"), row.names = c(1L, 3L, 4L, 5L, 6L, 7L, 8L,
9L, 10L, 11L, 12L, 13L, 14L, 15L), class = "data.frame"))
``````

No idea if this performs faster, but here's a shot at a data table method. I reshape `dt1` and use `findInterval` to identify where the times in `dt2` line up with times in `dt1`.

``````dt1 <- data.table(structure(list(circuit = structure(c(2L, 1L, 2L, 1L, 2L, 3L,
1L, 1L, 2L), .Label = c("a", "b", "c"), class = "factor"), start = structure(c(1393621200,
1393627920, 1393628400, 1393631520, 1393650300, 1393646400, 1393656000,
1393668000, 1393666200), class = c("POSIXct", "POSIXt"), tzone = ""),
end = structure(c(1393626600, 1393631519, 1393639200, 1393632000,
1393660500, 1393673400, 1393667999, 1393671600, 1393677000
), class = c("POSIXct", "POSIXt"), tzone = ""), id = structure(1:9, .Label = c("1001",
"1002", "1003", "1004", "1005", "1006", "1007", "1008", "1009"
), class = "factor")), .Names = c("circuit", "start", "end",
"id"), class = "data.frame", row.names = c(NA, -9L)))

dt2 <- data.table(structure(list(start = structure(c(1393621200, 1393624800, 1393626600,
1393627919, 1393628399, 1393632000, 1393639200, 1393646399, 1393650299,
1393655999, 1393660500, 1393666199, 1393671600, 1393673400), class = c("POSIXct",
"POSIXt"), tzone = ""), end = structure(c(1393624799, 1393626600,
1393627919, 1393628399, 1393632000, 1393639200, 1393646399, 1393650299,
1393655999, 1393660500, 1393666199, 1393671600, 1393673400, 1393677000
), class = c("POSIXct", "POSIXt"), tzone = ""), seconds = c(3599L,
1800L, 1319L, 480L, 3601L, 7200L, 7199L, 3900L, 5700L, 4501L,
5699L, 5401L, 1800L, 3600L), counts = c(1L, 1L, 0L, 1L, 2L, 1L,
0L, 1L, 2L, 3L, 2L, 3L, 2L, 1L)), .Names = c("start", "end",
"seconds", "counts"), row.names = c(1L, 3L, 4L, 5L, 6L, 7L, 8L,
9L, 10L, 11L, 12L, 13L, 14L, 15L), class = "data.frame"))

# > dt1
# circuit               start                 end   id
# 1:       b 2014-02-28 16:00:00 2014-02-28 17:30:00 1001
# 2:       a 2014-02-28 17:52:00 2014-02-28 18:51:59 1002
# 3:       b 2014-02-28 18:00:00 2014-02-28 21:00:00 1003
# 4:       a 2014-02-28 18:52:00 2014-02-28 19:00:00 1004
# 5:       b 2014-03-01 00:05:00 2014-03-01 02:55:00 1005
# 6:       c 2014-02-28 23:00:00 2014-03-01 06:30:00 1006
# 7:       a 2014-03-01 01:40:00 2014-03-01 04:59:59 1007
# 8:       a 2014-03-01 05:00:00 2014-03-01 06:00:00 1008
# 9:       b 2014-03-01 04:30:00 2014-03-01 07:30:00 1009

# > dt2
# start                 end seconds counts
# 1: 2014-02-28 16:00:00 2014-02-28 16:59:59    3599      1
# 2: 2014-02-28 17:00:00 2014-02-28 17:30:00    1800      1
# 3: 2014-02-28 17:30:00 2014-02-28 17:51:59    1319      0
# 4: 2014-02-28 17:51:59 2014-02-28 17:59:59     480      1
# 5: 2014-02-28 17:59:59 2014-02-28 19:00:00    3601      2
# 6: 2014-02-28 19:00:00 2014-02-28 21:00:00    7200      1
# 7: 2014-02-28 21:00:00 2014-02-28 22:59:59    7199      0
# 8: 2014-02-28 22:59:59 2014-03-01 00:04:59    3900      1
# 9: 2014-03-01 00:04:59 2014-03-01 01:39:59    5700      2
# 10: 2014-03-01 01:39:59 2014-03-01 02:55:00    4501      3
# 11: 2014-03-01 02:55:00 2014-03-01 04:29:59    5699      2
# 12: 2014-03-01 04:29:59 2014-03-01 06:00:00    5401      3
# 13: 2014-03-01 06:00:00 2014-03-01 06:30:00    1800      2
# 14: 2014-03-01 06:30:00 2014-03-01 07:30:00    3600      1

## reshapes dt1 from wide to long
## puts start and end times into one column and sorts by time
## this is so that you can use findInterval later
dt3 <- dt1[,list(time = c(start,end)), by = "circuit,id"][order(time)]
dt3[,ntvl := seq_len(nrow(dt3))]
# circuit   id                time ntvl
# 1:       b 1001 2014-02-28 16:00:00    1
# 2:       b 1001 2014-02-28 17:30:00    2
# 3:       a 1002 2014-02-28 17:52:00    3
# 4:       b 1003 2014-02-28 18:00:00    4
# 5:       a 1002 2014-02-28 18:51:59    5
# 6:       a 1004 2014-02-28 18:52:00    6
# 7:       a 1004 2014-02-28 19:00:00    7
# 8:       b 1003 2014-02-28 21:00:00    8
# 9:       c 1006 2014-02-28 23:00:00    9
# 10:       b 1005 2014-03-01 00:05:00   10
# 11:       a 1007 2014-03-01 01:40:00   11
# 12:       b 1005 2014-03-01 02:55:00   12
# 13:       b 1009 2014-03-01 04:30:00   13
# 14:       a 1007 2014-03-01 04:59:59   14
# 15:       a 1008 2014-03-01 05:00:00   15
# 16:       a 1008 2014-03-01 06:00:00   16
# 17:       c 1006 2014-03-01 06:30:00   17
# 18:       b 1009 2014-03-01 07:30:00   18

## map interval to id
dt4 <- dt3[,list(ntvl = seq(from = min(ntvl), to = max(ntvl)-1), by = 1),by = "circuit,id"]
setkey(dt4, ntvl)
# circuit   id ntvl
# 1:       b 1001    1
# 2:       a 1002    3
# 3:       a 1002    4
# 4:       b 1003    4
# 5:       b 1003    5
# 6:       b 1003    6
# 7:       a 1004    6
# 8:       b 1003    7
# 9:       c 1006    9
# 10:       c 1006   10
# 11:       b 1005   10
# 12:       c 1006   11
# 13:       b 1005   11
# 14:       a 1007   11
# 15:       c 1006   12
# 16:       a 1007   12
# 17:       c 1006   13
# 18:       a 1007   13
# 19:       b 1009   13
# 20:       c 1006   14
# 21:       b 1009   14
# 22:       c 1006   15
# 23:       b 1009   15
# 24:       a 1008   15
# 25:       c 1006   16
# 26:       b 1009   16
# 27:       b 1009   17
# circuit   id ntvl

## finds intervals in dt2
dt2[,`:=`(ntvl_start = findInterval(start, dt3[["time"]], rightmost.closed = FALSE),
ntvl_end = findInterval(end, dt3[["time"]], rightmost.closed = FALSE))]
# start                 end seconds counts ntvl_start ntvl_end
# 1: 2014-02-28 16:00:00 2014-02-28 16:59:59    3599      1          1        1
# 2: 2014-02-28 17:00:00 2014-02-28 17:30:00    1800      1          1        2
# 3: 2014-02-28 17:30:00 2014-02-28 17:51:59    1319      0          2        2
# 4: 2014-02-28 17:51:59 2014-02-28 17:59:59     480      1          2        3
# 5: 2014-02-28 17:59:59 2014-02-28 19:00:00    3601      2          3        7
# 6: 2014-02-28 19:00:00 2014-02-28 21:00:00    7200      1          7        8
# 7: 2014-02-28 21:00:00 2014-02-28 22:59:59    7199      0          8        8
# 8: 2014-02-28 22:59:59 2014-03-01 00:04:59    3900      1          8        9
# 9: 2014-03-01 00:04:59 2014-03-01 01:39:59    5700      2          9       10
# 10: 2014-03-01 01:39:59 2014-03-01 02:55:00    4501      3         10       12
# 11: 2014-03-01 02:55:00 2014-03-01 04:29:59    5699      2         12       12
# 12: 2014-03-01 04:29:59 2014-03-01 06:00:00    5401      3         12       16
# 13: 2014-03-01 06:00:00 2014-03-01 06:30:00    1800      2         16       17
# 14: 2014-03-01 06:30:00 2014-03-01 07:30:00    3600      1         17       18

## joins, by start time, then by end time
## the commented out lines may be a better alternative
## if there are many NA values
setkey(dt2, ntvl_start)
dt_ans_start <- dt4[dt2, list(start,end,counts,id,circuit),nomatch = NA]
# dt_ans_start <- dt4[dt2, list(start,end,counts,id,circuit),nomatch = 0]
# dt_ans_start_na <- dt2[!dt4]
setkey(dt2, ntvl_end)
dt_ans_end <- dt4[dt2, list(start,end,counts,id,circuit),nomatch = NA]
# dt_ans_end <- dt4[dt2, list(start,end,counts,id,circuit),nomatch = 0]
# dt_ans_end_na <- dt2[!dt4]

## bring them all together and remove duplicates
dt_ans <- unique(rbind(dt_ans_start, dt_ans_end), by = c("start", "id"))
dt_ans <- dt_ans[!(is.na(id) & counts > 0)]
dt_ans[,ntvl := NULL]
setkey(dt_ans,start)
# start                 end counts   id circuit
# 1: 2014-02-28 16:00:00 2014-02-28 16:59:59      1 1001       b
# 2: 2014-02-28 17:00:00 2014-02-28 17:30:00      1 1001       b
# 3: 2014-02-28 17:30:00 2014-02-28 17:51:59      0   NA      NA
# 4: 2014-02-28 17:51:59 2014-02-28 17:59:59      1 1002       a
# 5: 2014-02-28 17:59:59 2014-02-28 19:00:00      2 1002       a
# 6: 2014-02-28 17:59:59 2014-02-28 19:00:00      2 1003       b
# 7: 2014-02-28 19:00:00 2014-02-28 21:00:00      1 1003       b
# 8: 2014-02-28 21:00:00 2014-02-28 22:59:59      0   NA      NA
# 9: 2014-02-28 22:59:59 2014-03-01 00:04:59      1 1006       c
# 10: 2014-03-01 00:04:59 2014-03-01 01:39:59      2 1006       c
# 11: 2014-03-01 00:04:59 2014-03-01 01:39:59      2 1005       b
# 12: 2014-03-01 01:39:59 2014-03-01 02:55:00      3 1006       c
# 13: 2014-03-01 01:39:59 2014-03-01 02:55:00      3 1005       b
# 14: 2014-03-01 01:39:59 2014-03-01 02:55:00      3 1007       a
# 15: 2014-03-01 02:55:00 2014-03-01 04:29:59      2 1006       c
# 16: 2014-03-01 02:55:00 2014-03-01 04:29:59      2 1007       a
# 17: 2014-03-01 04:29:59 2014-03-01 06:00:00      3 1006       c
# 18: 2014-03-01 04:29:59 2014-03-01 06:00:00      3 1007       a
# 19: 2014-03-01 04:29:59 2014-03-01 06:00:00      3 1009       b
# 20: 2014-03-01 06:00:00 2014-03-01 06:30:00      2 1006       c
# 21: 2014-03-01 06:00:00 2014-03-01 06:30:00      2 1009       b
# 22: 2014-03-01 06:30:00 2014-03-01 07:30:00      1 1009       b
# start                 end counts   id circuit
``````
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