[英]Join 2 dataframes together if two columns match
I have 2 dataframes: 我有2个数据框:
CountryPoints 乡村积分
From.country To.Country points
Belgium Finland 4
Belgium Germany 5
Malta Italy 12
Malta UK 1
and another dataframe with neighbouring/bordering countries: 以及与邻国/邻国的另一个数据框:
From.country To.Country
Belgium Finland
Belgium Germany
Malta Italy
I would like to add another column in CountryPoints called neighbour (Y/N) depending if the key value pair is found in the neighbour/bordering countries dataframe. 我想在CountryPoints中添加另一列称为邻居(Y / N),具体取决于是否在邻居/边界国家/地区数据框中找到了键值对。 Is this somehow possible - so it is a kind of a join but the result should be a boolean column.
这有可能吗-所以它是一种联接,但结果应该是一个布尔列。
The result should be: 结果应为:
From.country To.Country points Neighbour
Belgium Finland 4 Y
Belgium Germany 5 Y
Malta Italy 12 Y
Malta UK 1 N
In the question below it shows how you can merge but it doesn't show how you can add that extra boolean column 在下面的问题中,它显示了如何合并,但未显示如何添加该额外的布尔列
Two alternative approaches: 两种替代方法:
1) with base R: 1)使用基数R:
idx <- match(df1$From.country, df2$From.country, nomatch = 0) &
match(df1$To.Country, df2$To.Country, nomatch = 0)
df1$Neighbour <- c('N','Y')[1 + idx]
2) with data.table
: 2)与
data.table
:
library(data.table)
setDT(df1)
setDT(df2)
df1[, Neighbour := 'N'][df2, on = .(From.country, To.Country), Neighbour := 'Y'][]
which both give ( data.table
-output shown): 两者都给出(显示了
data.table
):
From.country To.Country points Neighbour 1: Belgium Finland 4 Y 2: Belgium Germany 5 Y 3: Malta Italy 12 Y 4: Malta UK 1 N
What about something like this? 那这样的东西呢?
sortpaste <- function(x) paste0(sort(x), collapse = "_");
df1$Neighbour <- apply(df1[, 1:2], 1, sortpaste) %in% apply(df2[, 1:2], 1, sortpaste)
# From.country To.Country points Neighbour
#1 Belgium Finland 4 TRUE
#2 Belgium Germany 5 TRUE
#3 Malta Italy 12 TRUE
#4 Malta UK 1 FALSE
df1 <- read.table(text =
"From.country To.Country points
Belgium Finland 4
Belgium Germany 5
Malta Italy 12
Malta UK 1", header = T)
df2 <- read.table(text =
"From.country To.Country
Belgium Finland
Belgium Germany
Malta Italy", header = T)
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