问题描述
我几乎到处都找遍了,但找不到答案;R 相当于 Excel 上的 VLOOKUP.VLOOKUP 允许我在整个列中查找特定值并将其应用于数据框的每一行.
I have looked pretty much everywhere and cannot find the answer to this; R equivalent of VLOOKUP on Excel. VLOOKUP allows me to look up for a specific value throughout a column and apply it to each row of my data frame.
在这种情况下,我想查找特定城市所在的国家/地区(从数据库中)并在新列中返回该国家/地区的名称.
In this case I want to find the country a particular city is in (from a database) and return the name of the country in a new column.
所以我有这个数据库:
countries <- c("UK", "US", "RUS")
cities <- c("LDN", "NY", "MOSC")
db <- cbind(countries, cities)
db
countries cities
[1,] "UK" "LDN"
[2,] "US" "NY"
[3,] "RUS" "MOSC"
并想根据上面的数据库找到这些城市所在的国家(替换 NA):
And want to find the country those cities are in (replace NA) based on the db above:
df
countries cities
[1,] NA "LDN"
[2,] NA "NY"
[3,] NA "MOSC"
我完全不知道如何在 R 上解决这个问题.
I have absolutely no idea how to go about this on R.
推荐答案
您正在执行 join 在 R 中使用 merge
merge(db, df)
使用 dplyr
包允许更自然的动词:
Using the dplyr
package allows more natural verbs:
library(dplyr)
inner_join(db, df)
或者(如果您希望显示不匹配的内容;请参阅 ?left_join
了解更多信息):
or perhaps (if you want non-matches to be shown; see ?left_join
for further information):
left_join(db, df)
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