8.3 Primer to joins

library(dplyr)
## 
## Attaching package: 'dplyr'
## The following objects are masked from 'package:stats':
## 
##     filter, lag
## The following objects are masked from 'package:base':
## 
##     intersect, setdiff, setequal, union

# use double colon to specify which library you are getting a function from
# base::union()

table4a_tidy
## # A tibble: 6 x 3
##   country     year   cases
##   <chr>       <chr>  <int>
## 1 Afghanistan 2000    2666
## 2 Brazil      2000   80488
## 3 China       2000  213766
## 4 Afghanistan 1999     745
## 5 Brazil      1999   37737
## 6 China       1999  212258

table4b_tidy
## # A tibble: 6 x 3
##   country     year  population
##   <chr>       <chr>      <int>
## 1 Afghanistan 1999    19987071
## 2 Brazil      1999   172006362
## 3 China       1999  1272915272
## 4 Afghanistan 2000    20595360
## 5 Brazil      2000   174504898
## 6 China       2000  1280428583

left_join(x = table4a_tidy, y = table4b_tidy)
## Joining, by = c("country", "year")
## # A tibble: 6 x 4
##   country     year   cases population
##   <chr>       <chr>  <int>      <int>
## 1 Afghanistan 2000    2666   20595360
## 2 Brazil      2000   80488  174504898
## 3 China       2000  213766 1280428583
## 4 Afghanistan 1999     745   19987071
## 5 Brazil      1999   37737  172006362
## 6 China       1999  212258 1272915272