Question

我试图在两个表之间进行复杂的非等连接。我在最后一次使用R2016（https://channel9.msdn.com/events/useR-international-R-User-conference/useR2016/Efficient-in-memory-non-equi-joins-using-datatable）中的演示中受到启发，这让我相信它对data.table来说是一个合适的任务。我的表1看起来像：

library(data.table)
sp <- c("SAB","SAB","SAB","SAB","EPN","EPN","BOP","BOP","BOP","BOP","BOP","PET","PET","PET")
dbh <- c(10,12,16,22,12,16,10,12,14,20,26,12,16,18)
dt1 <- data.table(sp,dbh)
dt1
     sp dbh
 1: SAB  10
 2: SAB  12
 3: SAB  16
 4: SAB  22
 5: EPN  12
 6: EPN  16
 7: BOP  10
 8: BOP  12
 9: BOP  14
10: BOP  20
11: BOP  26
12: PET  12
13: PET  16
14: PET  18

它是dbh的树木列表。我的第二个表（下面）给出了一个通用表，它为每个树种提供了一系列dbh来对大小类或树进行分类：

gr_sp <- c("RES","RES","RES","RES","RES","RES", "DEC", "DEC", "DEC", "DEC", "DEC", "DEC")
sp <- c("SAB","SAB", "SAB", "EPN", "EPN", "EPN", "BOP", "BOP", "BOP", "PET", "PET", "PET")
dbh_min <- c(10, 16, 22, 10, 14, 20, 10, 18, 24, 10, 20, 26)
dbh_max <- c(14, 20, 30, 12, 18, 30, 16, 22, 30, 18, 24, 30)
dhb_clas <- c("s", "m", "l", "s", "m", "l", "s", "m", "l", "s", "m", "l")

dt2 <- data.table(gr_sp, sp, dbh_min, dbh_max, dhb_clas)
dt2
    gr_sp  sp dbh_min dbh_max dhb_clas
 1:   RES SAB      10      14        s
 2:   RES SAB      16      20        m
 3:   RES SAB      22      30        l
 4:   RES EPN      10      12        s
 5:   RES EPN      14      18        m
 6:   RES EPN      20      30        l
 7:   DEC BOP      10      16        s
 8:   DEC BOP      18      22        m
 9:   DEC BOP      24      30        l
10:   DEC PET      10      18        s
11:   DEC PET      20      24        m
12:   DEC PET      26      30        l

我希望我的最终表格能够按物种（＆＃34; sp＆＃34;字段）连接两个表格，并且在＆＃34; DBH_MIN＆＃34;所示的dhb范围内。和＆＃34; DBH_MAX＆＃34;。这会使我的表看起来像：

data.table(dt1, gr_sp = c("RES","RES","RES","RES","RES","RES","DEC","DEC","DEC","DEC","DEC","DEC","DEC","DEC"), dhb_clas = c("s","s","m","l","s","m","s","s","s","m","l","s","s","s"))
     sp dbh gr_sp dhb_clas
 1: SAB  10   RES        s
 2: SAB  12   RES        s
 3: SAB  16   RES        m
 4: SAB  22   RES        l
 5: EPN  12   RES        s
 6: EPN  16   RES        m
 7: BOP  10   DEC        s
 8: BOP  12   DEC        s
 9: BOP  14   DEC        s
10: BOP  20   DEC        m
11: BOP  26   DEC        l
12: PET  12   DEC        s
13: PET  16   DEC        s
14: PET  18   DEC        s

我尝试过类似的事情：

dt1[dt2, on=.(sp=sp, dbh>=dbh_min, dbh<=dbh_max)]

这会产生太多行...

感谢您的帮助

Answer 1

所以我非常接近。我遇到了2个问题，首先是data.table包（Data table error could not find function "."）的错误安装导致了一个模糊的错误。

在解决了这个问题之后，我发现了一个发现：

dt1[dt2, on=.(sp=sp, dbh>=dbh_min, dbh<=dbh_max), nomatch=0]

用一个糟糕的dbh列给了我想要的东西。使用以下命令反转命令：

dt2[dt1, on=.(sp=sp, dbh_min<=dbh, dbh_max>=dbh)]

只用一个无用的额外列修复了问题。

Answer 2

对于像这样的“之间”联接，也可以使用data.table::foverlaps，它在重叠的范围内联接两个data.table，而不是使用非等联接。

以同一示例为例，以下代码将产生所需的结果。

# foverlap tests the overlap of two ranges.  Create a second column,
# dbh2, as the end point of the range.
dt1[, dbh2 := dbh]

# foverlap requires the second argument to be keyed
setkey(dt1, sp, dbh, dbh2)

# find rows where dbh falls between dbh_min and dbh_max, and drop unnecessary
# columns afterwards
foverlaps(dt2, dt1, by.x = c("sp", "dbh_min", "dbh_max"), by.y = key(dt1),
          nomatch = 0)[
  ,
  -c("dbh2", "dbh_min", "dbh_max")
]

#  sp dbh gr_sp dhb_clas
#  1: SAB  10   RES        s
#  2: SAB  12   RES        s
#  3: SAB  16   RES        m
#  4: SAB  22   RES        l
#  5: EPN  12   RES        s
#  6: EPN  16   RES        m
#  7: BOP  10   DEC        s
#  8: BOP  12   DEC        s
#  9: BOP  14   DEC        s
# 10: BOP  20   DEC        m
# 11: BOP  26   DEC        l
# 12: PET  12   DEC        s
# 13: PET  16   DEC        s
# 14: PET  18   DEC        s

R中的Complexe非equi合并

2 个答案: