在循环中检查特定的对象名称

Question

I have a loop with a lot of data frames.

When I come to certain data frames my logic needs to adjust. I'm looking for a while to make a TRUE/FALSE statement out of this, but I'm not sure exactly how to pull this off.

I want to convert the actual name of the variable into the text of the variable.

my_list_of_dfs = list(iris,mtcars)

for (i in my_list_of_dfs){ if i =='iris'{ print('this works') } }

Answer 1

Try a named list instead

# Created a named list instead...
my_list_of_dfs = list('iris'=iris, 'mtcars'=mtcars)

# check the names
names(my_list_of_dfs)
# [1] "iris"   "mtcars"

for (i in names(my_list_of_dfs) ) {
  if (i =='iris') {
    print('this works')
  }
  print (my_list_of_dfs[i]) # You can access data-frame like this...
}

BTW, you also forgot the brackets around the condition in your if statement

Answer 2

An addition to answer by @Ismail (so please upvote that answer if you agree with the idea of using a named list), is to create a function that generates a named list for you. That is, instead of explicitly typing something like list('iris'=iris, 'mtcars'=mtcars) , the following function will take R objects, combine them in a list, and name the list with the objects:

named_list <- function(...) {
  .l <- list(...)
  .names <- deparse(substitute(list(...)))
  .names <- strsplit(gsub("list\\(|\\)| ", "", .names), ",")[[1]]
  names(.l) <- .names
  .l
}

x <- 3
y <- data.frame(a=1,b=2)
named_list(x, y)
#> $x
#> [1] 3
#> 
#> $y
#>   a b
#> 1 1 2

my_list_of_dfs  <- named_list(iris, mtcars)
names(my_list_of_dfs )
#> [1] "iris"   "mtcars"

Can follow @Ismail answer from here with something like:

for (i in names(my_list_of_dfs )) {
  if (i == "iris")
    print(names(my_list_of_dfs[[i]]))
  else
    print ("This is NOT iris")
}
#> [1] "Sepal.Length" "Sepal.Width"  "Petal.Length" "Petal.Width" "Species"     
#> [1] "This is NOT iris"