需要协助以了解R的循环错误：“”中意外的'}'

Question

Just to give some background first:

I currently have 2 data frames (giraffe, leaf) and both of them share the column 'key', where the elements in the leaf data frame are a subset of giraffe. What I needed to do is compare the two data frames and when there are matching elements in both data frames in the 'key' column, the string 'leaf' will be input into another column (project) in the giraffe data frame inside the same row as the matching 'key' element. I've taken the following approach however it seems I have made a small error somewhere and after searching online, I still don't know what it is:

Truth_vector <- is.element((giraffe[,1]),(leaf[,1])) #returns a vector with 3000 elements, most are FALSE except for where the element inside 'key' is present in both data frames

i=1
for (i in 1:length(giraffe[,1])) {
  if Truth_vector[i] == TRUE {
   giraffe[i,5] <- 'leaf'
  }
  i = i+1
}

Error: unexpected '}' in "}"

Edit:

I tried implementing the solution as a function however nothing ends up happening, no error messages get returned either. What I've done is:

Project_assign <- function(prjct) {
Truth_vector <- is.element((giraffe[,1]),(prjct[,1]))
giraffe[which(Truth_vector),5] <- 'prjct'
}
Project_assign(leaf)

Edit: This was because everything was getting assigned in the function sub environment, not the global environment. Using assign('giraffe',giraffe,envir=.GlobalEnv) solves this however you should try and avoid the assign function and Instead I used a for loop going over a list of all the dataframes

Answer 1

You have a couple issues. First, the if criteria needs to be in parentheses, and secondly you don't need to increment i yourself. This should suffice:

for (i in 1:length(giraffe[,1])) {
  if (Truth_vector[i] == TRUE) {
   giraffe[i,5] <- 'leaf'
  }
}

Of course, this would do it too:

giraffe[which(Truth_vector),5] <- 'leaf'

(assuming Truth_vector is not longer than the number of rows in giraffe)