I'm using RStudio, and I have one dataframe containing a list of candidates, and a dataframe containing all votes of each voting location, and by candidate.

I want to extract only the rows containing the votes of the candidates of this list.

Example:

• List:

   Candidate
   A
   B
   D
   G
  

• Votes:

   Candidate       Number of Votes
   A               124
   B               52
   C               13
   D               62
   E               33
   F               7
   G               67
  

I want then to create a new dataframe containing only the candidates and votes of the "List":

• Votes of listed candidates:

   Candidate       Number of Votes
   A               124
   B               52
   D               62
   G               67
  

The example is a simplification. My database contains over 30.000 "candidates"

Thanks in advance

CodePudding user response：

We can use subset in base R

subset(Votes, Candidate %in% List$Candidate)

CodePudding user response：

You can merge both data frames with merge():

merge(df1, df2, by = "Candidate", all.x = TRUE)

or equivalently

dplyr::left_join(df1, df2, by = "Candidate")

#   Candidate Number_of_Votes
# 1         A             124
# 2         B              52
# 3         D              62
# 4         G              67

Data

df1 <- structure(list(Candidate = c("A", "B", "D", "G")), class = "data.frame", row.names = c(NA, -4L))
df2 <- structure(list(Candidate = c("A", "B", "C", "D", "E", "F", "G"),
Number_of_Votes = c(124L, 52L, 13L, 62L, 33L, 7L, 67L)), class = "data.frame", row.names = c(NA, -7L))