Replacing values in a column where there is a match

Question

I\'m new to R programming and I\'m stuck on the example below.

Basically I have two data sets:

dataset1:

ID       Category        
1        CatZ         


        

Answer 1

You can stack df2 on top of df1 and keep the first instance for each ID.

With tidyverse that would be :

library(tidyverse)
bind_rows(df2,df1) %>%
  group_by(ID) %>%
  slice(1) %>%
  ungroup()

# # A tibble: 4 x 2
#      ID Category
#       
# 1     1   Cat600
# 2     2    CatVV
# 3     3   Cat611
# 4     4    CatQQ

Or a base version (which reorders the rows) :

subset(rbind(df2,df1), !duplicated(ID))
#   ID Category
# 1  1   Cat600
# 2  3   Cat611
# 4  2    CatVV
# 6  4    CatQQ