Joining sf object with data (3)

left_join(x, y, by = "a")

## Simple feature collection with 2 features and 2 fields
## Geometry type: POINT
## Dimension:     XY
## Bounding box:  xmin: 0 ymin: 0 xmax: 1 ymax: 1
## CRS:           NA
##   a letter        geom
## 1 1   <NA> POINT (0 0)
## 2 2      k POINT (1 1)