zx8754 zx8754 - 2 months ago 17
R Question

dplyr::select one column and output as vector

dplyr::select
results in a data.frame, is there a way to make it return a vector if the result is one column?

Currently, I have to do extra step (
res <- res$y
) to convert it to vector from data.frame, see this example:

#dummy data
df <- data.frame(x = 1:10, y = LETTERS[1:10], stringsAsFactors = FALSE)

#dplyr filter and select results in data.frame
res <- df %>% filter(x > 5) %>% select(y)
class(res)
#[1] "data.frame"

#desired result is a character vector
res <- res$y
class(res)
#[1] "character"


Something as below:

res <- df %>% filter(x > 5) %>% select(y) %>% as.character
res
# This gives strange output
[1] "c(\"F\", \"G\", \"H\", \"I\", \"J\")"

# I need:
# [1] "F" "G" "H" "I" "J"

Answer

The best way to do it (IMO):

library(dplyr)
df <- data_frame(x = 1:10, y = LETTERS[1:10])

df %>% 
  filter(x > 5) %>% 
  .$y
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