dplyr::选择一列并输出为向量 [英] dplyr::select one column and output as vector
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问题描述
dplyr::select
结果是一个 data.frame,如果结果是一列,有没有办法让它返回一个向量?
dplyr::select
results in a data.frame, is there a way to make it return a vector if the result is one column?
目前,我必须执行额外的步骤 (res <- res$y
) 才能将其从 data.frame 转换为向量,请参阅此示例:
Currently, I have to do extra step (res <- res$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$y
class(res)
#[1] "character"
如下:
res <- df %>% filter(x > 5) %>% select(y) %>% as.character
res
# This gives strange output
[1] "c("F", "G", "H", "I", "J")"
# I need:
# [1] "F" "G" "H" "I" "J"
推荐答案
最好的方法 (IMO):
The best way to do it (IMO):
library(dplyr)
df <- data_frame(x = 1:10, y = LETTERS[1:10])
df %>%
filter(x > 5) %>%
.$y
<小时>
在 dplyr 0.7.0 中,您现在可以使用 pull():
In dplyr 0.7.0, you can now use pull():
df %>% filter(x > 5) %>% pull(y)
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