dataframe - r add columns in df1 with count of rows in df2 (conditional) -


i have 2 data frames in r below...i need add new column(count_orders) in df1 contains count of orders in df2 (or count of buyer in df2). please help.

> df1   buyer city 1       xx 2     b   yy 3     c   zz > df2   order buyer item 1     1        1 2     2        2 3     3     b    1 4     4        2 5     5     b    1 6     6     c    3 7     7     c    4

expected output:

> df1   buyer city count_orders 1       xx   3 2     b   yy   2 3     c   zz   2

here's dplyr approach:

library(dplyr) count(df2, buyer) %>% right_join(df1, "buyer") #source: local data frame [3 x 3] # #  buyer n city #1     3   xx #2     b 2   yy #3     c 2   zz

you use count(df2, buyer) %>% right_join(df1) , let dplyr figure out column join on own ("buyer" in case).


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