连接具有不同观察数量的两个数据集

Question

I have two datasets that contain the population and the longitude/latitude of subregions. Since there are several geographical entries per subregion, I want to join these datasets in a way that the population is displayed in every single corresponding geographical row. I have tried every dplyr command (inner_join, full_join etc) but can't make it work. Any help on this is greatly appreciated!

Dataset 1 (100 observations)

subregion    population 

adams        66949
alexander     7051
bond         17137
...          ...

Dataset 2 (10000 observations)

subregion   longitude   latitude

adams       -91.49563    40.21018
adams       -90.91121    40.19299
adams       -90.91694    39.75754
alexander   -89.20380    37.32247
...         ...          ...

Desired dataset

subregion   longitude   latitude   population

adams       -91.49563    40.21018  66949
adams       -90.91121    40.19299  66949
adams       -90.91694    39.75754  66949
alexander   -89.20380    37.32247   7051
...         ...          ...

Answer 1

#library(tibble) # uncomment if needed to access tribble()

B <- tribble(  # Using tribble to make quick, easy df's from your post
  ~subregion,    ~population ,
  "adams",        66949,
  "alexander",     7051,
  "bond",         17137)

A <- tribble(
  ~subregion,   ~longitude,   ~latitude,
  "adams",       -91.49563,    40.21018,
  "adams",       -90.91121,    40.19299,
  "adams",       -90.91694,    39.75754,
  "alexander",   -89.20380,    37.32247)

merge(A,B,by="subregion")

#> merge(A,B,by="subregion")
#  subregion longitude latitude population

#1     adams -91.49563 40.21018      66949
#2     adams -90.91121 40.19299      66949
#3     adams -90.91694 39.75754      66949
#4 alexander -89.20380 37.32247       7051

NOTE: Bond is dropped. Use

merge(A,B,by="subregion",all.x=TRUE,all.y=TRUE) 

if bond's pop is required but lat/long not (vals will be set to NA).

One may keep all from the first frame or the second frame or both (padding with NAs) with the various combos of all.x/all.y set to TRUE or FALSE.