根据R中的条件合并2个数据帧

Question

I have the following 2 data frames that I want to merge:

x <- data.frame(a= 1:11, b =3:13, c=2:12, d=7:17, invoice = 1:11)
x =
   a  b  c  d invoice
   1  3  2  7       1
   2  4  3  8       2
   3  5  4  9       3
   4  6  5 10       4
   5  7  6 11       5
   6  8  7 12       6
   7  9  8 13       7
   8 10  9 14       8
   9 11 10 15       9
  10 12 11 16      10
  11 13 12 17      11


y <- data.frame(nr = 100:125, invoice = 1)
y$invoice[12:26] <- 2

> y
    nr invoice
   100       1
   101       1
   102       1
   103       1
   104       1
   105       1
   106       1
   107       1
   108       1
   109       1
   110       1
   111       2
   112       2
   113       2
   114       2
   115       2
   116       2
   117       2

I want to merge the letters from dataframe X with dataframe Y when the invoice number is the same. It should start with merging the value from letter A, then B ect. This should be happening until the invoice number is not the same anymore and then choose the numbers from invoice nr 2.

the output should be like this:

> output
    nr invoice  letter_count
   100       1    1
   101       1    3
   102       1    2
   103       1    7
   104       1    1
   105       1    3
   106       1    2
   107       1    7
   108       1    1
   109       1    2
   110       1    7
   111       2    2
   112       2    4
   113       2    3
   114       2    8
   115       2    2
   116       2    4

I tried to use the merge function with the by argument but this created an error that the number of rows is not the same. Any help I will appreciate.

Answer 1

Here is a solution using the purrr package.

# Prepare the data frames
x <- data.frame(a = 1:11, b = 3:13, c = 2:12, d = 7:17, invoice = 1:11)
y <- data.frame(nr = 100:125, invoice = 1)
y$invoice[12:26] <- 2

# Load package
library(purrr)

# Split the data based on invoice
y_list <- split(y, f = y$invoice)

# Design a function to transfer data
trans_fun <- function(main_df, letter_df = x){

  # Get the invoice number
  temp_num<- unique(main_df$invoice)
  # Extract letter_count information from x
  add_vec <- unlist(letter_df[letter_df$invoice == temp_num, 1:4])
  # Get the remainder of nrow(main_df) and length(add_vec)
  reamin_num <- nrow(main_df) %% length(add_vec)
  # Get the multiple of nrow(main_df) and length(add_vec)
  multiple_num <- nrow(main_df) %/% length(add_vec)
  # Create the entire sequence to add
  add_seq <- rep(add_vec, multiple_num + 1)
  add_seq2 <- add_seq[1:(length(add_seq) - (length(add_vec) - reamin_num))]
  # Add new column, add_seq2, to main_df
  main_df$letter_count <- add_seq2

  return(main_df)
}

# Apply the trans_fun function using map_df 
output <- map_df(y_list, .f = trans_fun)

# See the result
output
    nr invoice letter_count
1  100       1            1
2  101       1            3
3  102       1            2
4  103       1            7
5  104       1            1
6  105       1            3
7  106       1            2
8  107       1            7
9  108       1            1
10 109       1            3
11 110       1            2
12 111       2            2
13 112       2            4
14 113       2            3
15 114       2            8
16 115       2            2
17 116       2            4
18 117       2            3
19 118       2            8
20 119       2            2
21 120       2            4
22 121       2            3
23 122       2            8
24 123       2            2
25 124       2            4
26 125       2            3