r - 通过匹配给定因子水平的变量/列选择数据框中的变量/列

Question

是否可以通过匹配特定因子水平的那些来选择数据框中的变量，根据它们的因子水平(使用或未使用)选择列？我可以summarise by levels或可能的子集 by rows ，但我想知道是否可以从数据框中选择列，或者至少列出具有特定因子水平的变量/列。

library(dplyr)
height <- c(132,151,162,139,166,147,122)
    weight <- c(48,49,66,53,67,52,40)
    gender <- c("male","male","female","female","male","female","male")
    gender2 <- c("female","male","male","male","male","female","male")
    genderx <- c("xfemale","malex","malex","male","male","xfemale","xfemale")


    df <- data.frame(height,weight,gender, gender2, genderx) %>% 
      rowid_to_column(., "ID")

喜欢(或不喜欢)的东西

%>% select (vars(levels ==(c("male", "female")))

Answer 1

我们可以使用select_if

library(dplyr)
df %>% 
    select_if(~ is.factor(.) && all(c("male", "female") %in% levels(.)))

也可以是任意

df %>% 
    select_if(~ is.factor(.) && any(c("male", "female") %in% levels(.)))