9.1 Create simple datasets

library(tibble)
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

x <- tribble(
    ~key, ~val_x,
    1, "x1",
    2, "x2",
    3, "x3"
)
x
## # A tibble: 3 x 2
##     key val_x
##   <dbl> <chr>
## 1     1 x1   
## 2     2 x2   
## 3     3 x3

y <- tribble(
    ~key, ~val_y,
    1, "y1",
    2, "y2",
    4, "y3"
)
y
## # A tibble: 3 x 2
##     key val_y
##   <dbl> <chr>
## 1     1 y1   
## 2     2 y2   
## 3     4 y3