Repeated values cause unexpected data lengthening when merging.
df1 <- data.frame(col1 = LETTERS[1:4],
col2 = 1:4)
df1 %>% kable() %>% kable_styling()
| col1 | col2 |
|---|---|
| A | 1 |
| B | 2 |
| C | 3 |
| D | 4 |
df2 <- data.frame(col1 = rep(LETTERS[1:2], 2),
col3 = 4:1)
df2 %>% kable() %>% kable_styling()
| col1 | col3 |
|---|---|
| A | 4 |
| B | 3 |
| A | 2 |
| B | 1 |
I might expect four rows after merging, but instead I get six.
df <- left_join(df1, df2)
df %>% kable() %>% kable_styling()
| col1 | col2 | col3 |
|---|---|---|
| A | 1 | 4 |
| A | 1 | 2 |
| B | 2 | 3 |
| B | 2 | 1 |
| C | 3 | NA |
| D | 4 | NA |
Bo\(^2\)m =)