When the “to-be-merged” column(s) do not currently exist in the main dataframe, use left join. When the “to-be-merged” info already has a column in the main dataframe, use if-else or case-when.
library(kableExtra)
library(tidyverse)
df1 <- data.frame(
'id' = c(1, 2, 3, 1, 2, 3, 1, 2, 3),
'match' = c('a', 'b', 'c', 'a', 'b', 'c', 'a', 'b', 'c')
)
df2 <- data.frame(
'match' = c('a', 'b'),
'intracker' = c('yes', 'yes')
)
df1 <- df1 %>% left_join(df2)
df1 %>% kable() %>% kable_styling()| id | match | intracker |
|---|---|---|
| 1 | a | yes |
| 2 | b | yes |
| 3 | c | NA |
| 1 | a | yes |
| 2 | b | yes |
| 3 | c | NA |
| 1 | a | yes |
| 2 | b | yes |
| 3 | c | NA |
df3 <- data.frame(
'match' = c('c'),
'intracker' = c('no')
)
df3 %>% kable() %>% kable_styling()| match | intracker |
|---|---|
| c | no |
Left join won’t work
df1 <- left_join(df1, df3)
df1 %>% kable() %>% kable_styling()| id | match | intracker |
|---|---|---|
| 1 | a | yes |
| 2 | b | yes |
| 3 | c | NA |
| 1 | a | yes |
| 2 | b | yes |
| 3 | c | NA |
| 1 | a | yes |
| 2 | b | yes |
| 3 | c | NA |
Mutate case-when works…
df1 <- data.frame(
'id' = c(1, 2, 3, 1, 2, 3, 1, 2, 3),
'match' = c('a', 'b', 'c', 'a', 'b', 'c', 'a', 'b', 'c')
)
df2 <- data.frame(
'match' = c('a', 'b'),
'intracker' = c('yes', 'yes')
)
df1 <- df1 %>% left_join(df2)
df1 <- df1 %>% mutate(intracker = case_when(
match == 'c' ~ df3$intracker,
TRUE ~ intracker
))
# or,
# df1 <- df1 %>% mutate(intracker = ifelse(match == 'c', df3$intracker, df1$intracker))
#
# the trick is whether the column already exists
df1 %>% kable() %>% kable_styling()| id | match | intracker |
|---|---|---|
| 1 | a | yes |
| 2 | b | yes |
| 3 | c | no |
| 1 | a | yes |
| 2 | b | yes |
| 3 | c | no |
| 1 | a | yes |
| 2 | b | yes |
| 3 | c | no |
Bo\(^2\)m =)