r - 考虑键列之间的范围匹配，合并两个数据框

Question

我是 R 编程的初学者。我目前正在尝试从包含 X 和 Y 坐标和站点名称的数据框中检索一些站点名称，并将它们复制到具有特定点的不同数据框中。

    FD <- matrix(data =c(rep(1, 500), rep(0, 500),
                     rnorm(1000, mean = 550000, sd=4000),
                     rnorm(1000, mean = 6350000, sd=20000), rep(NA, 1000)),
             ncol = 4, nrow = 1000, byrow = FALSE)
colnames(FD) <- c('Survival', 'X', 'Y', 'Site') 
FD <- as.data.frame(FD)

shpxt <- matrix(c(526654.7,526810.5 ,6309098,6309187,530405.4,530692,
                  6337699, 6338056,580432.7, 580541.9, 6380246,6380391,
                  585761.3, 585847.6, 6379665, 6379759, 584192.1, 584279.4,
                  6382358, 6382710, 583421.2, 583492.4, 6379356, 6379425,
                  532395.5, 532515.3 , 6336421, 6336587, 534694.6, 534791.2,
                  6335620, 6335740, 536749.8, 536957.5, 6337584, 6338130, 590049.6,
                  590419.4, 6372232, 6372432, 580443, 580756.5, 6386342, 6386473,
                  575263.9, 575413.7, 6380416, 6380530, 584625.1, 584753.9, 6381009,
                  6381335), ncol = 4, nrow = 13, byrow = TRUE)
sites <- c("Brandbaeltet", "Brusaa", "Granly", "Jerup Strand", "Knasborgvej",
           "Milrimvej", "Overklitten", "Oversigtsareal", "Sandmosen",
           "Strandby", "Troldkaer", "Vaagholt", "Videsletengen")
colnames(shpxt) <- c("Xmin", "Xmax", "Ymin", "Ymax")
shpxt <- as.data.frame(shpxt)
shpxt["Sites"] <- sites

我的方法是使用这样的嵌套 for 循环:

    tester <- function(FD, shpxt)
{ for (i in 1:nrow(FD)) for (j in 1:nrow(shpxt))         # Open Function
{ if (FD[i,2] >= shpxt[j,1] | FD[i,2] <= shpxt[j,2] &    # Open Loop
      FD[i,3] >= shpxt[j,3] | FD[i,3] <= shpxt[j,4])
{                                                        # Open Consequent
  FD[i,4]=shpxt[j,5]
  {break}
} else                                                  # Close Consequent
{FD[i,4] <- NA                                          # Open alternative
}                                                      # Close alternative
}                                                      # Close loop
}                                                      # Close function

tester(FD, shpxt)

本质上我想搜索FD中的X和Y坐标落在哪个站点范围内，并将站点名称复制到第i行的FD$Site中。当我在我的真实数据上运行循环时，我收到以下错误消息:

test(FD, shpxt)
Error in if (FD[i, 2] >= shpxt[j, 1] | FD[i, 2] <= shpxt[j, 2] & FD[i,  : 
  missing value where TRUE/FALSE needed

我如何让循环从此处转到循环将所需站点名称复制到我的 FD 的位置？

亲切的问候Thøger

Answer 1

考虑到键列之间的范围匹配，您想合并两个数据框。这里有两个解决方案。

使用sqldf

library(sqldf)

output <- sqldf("select * from FD left join shpxt 
                on (FD.X >= shpxt.Xmin and FD.X <= shpxt.Xmax and
                    FD.Y >= shpxt.Ymin and FD.Y <= shpxt.Ymax ) ")

使用data.table

library(data.table)

# convert your datasets in data.table
  setDT(FD) 
  setDT(shpxt)

output <- FD[shpxt, on = .(X >= Xmin , X <= Xmax,                # indicate x range
                           Y >= Ymin , Y <= Ymax), nomatch = NA, # indicate y range
             .(Survival, X, Y, Xmin, Xmax, Ymin, Ymax, Sites )]  # indicate columns in the output

有不同的替代方案可以解决这个问题，您会在其他 SO 问题中找到它 here和 here .

附言。请记住，for 循环 不一定是最佳解决方案。