加入并匹配R中的两个数据框

Question

I have two data frames. The first data frame consists of: four columns 1) ID, 2) Site, 3) Depth, and 3) Density. The second data frame consists of 3 columns: 1) ID, 2) Site and 3) Choice (ie, favorite site).

df1

  ID  Site Depth Density      
  1     B   0.1       0
  2     C   0.2       0
  3     C   0.2       1
  4     A  0.05       0
  5     A  0.05       1
  6     B   0.1       1
  7     B   0.1       2
  8     B   0.1       3
  9     D   0.3       0
 10     C   0.2       2
 11     D   0.3       1
 12     D   0.3       2
 13     D   0.3       3
 14     D   0.3       4
 15     D   0.3       5

df 2

     ID     Site   Choices
      1       A     No
      1       B     Yes
      1       C     No
      1       D     No
      2       A     No
      2       B     No
      2       C     Yes
      2       D     No
      3       A     No
      3       B     No
      3       C     Yes
      3       D     No
      4       A     Yes
      4       B     No
      4       C     No
      4       D     No

I am trying to add a column to df2 that has the densities of each ID at each site when an ID selected its favorite site.

Desired Output:

     ID     Site   Depth  Density    Choice
      1       A      0.05     0         No
      1       B      0.1      0         Yes
      1       C      0.2      0         No
      1       D      0.3      0         No
      2       A      0.05     0         No
      2       B      0.1      1         No
      2       C      0.2      0         Yes
      2       D      0.3      0         No
      3       A      0.05     0         No
      3       B      0.1      0         No
      3       C      0.2      1         Yes
      3       D      0.3      0         No
      4       A      0.05     0         Yes
      4       B      0.1      1         No
      4       C      0.2      2         No
      4       D      0.3      0         No

df2 explanation: When ID 1 selected site B, there was 0 density in site A,B,C, and D. When ID 2 selected C, the density in site A was 0, in site B 1, in site C 0, and site D 0. When ID 3 selected site C, the density in A was still 0 (no ID has chosen site A yet), B has 1, C has 1, and site D 0, and so on.

I've tried using the full join function and mutate function but I am not getting my desired output:

           df3<-df2 %>%
           full_join(df1, by = c("ID", "Site")) %>%
           group_by(ID) %>%
           mutate(Density= Density[Choice == "Yes"] ) %>%
           distinct(ID, Site, .keep_all = TRUE)

Answer 1

I think Density is the running total of how many groups have selected each site. To calculate that, I would do this:

df3 <- df2 %>%
  full_join(df1, by = c("ID", "Site")) %>%
  arrange(ID, site) %>%  ## make sure IDs are in ascending order
  group_by(Site) %>%
  mutate(Density = cumsum(Choice == "Yes"))