用ggplot2和dplyr编程

我想使用管道将dplyr和ggplot组合在一个函数中，并且现在遇到了一些问题.

I want to combine dplyr and ggplot within one function using piping and struggling with some issues now.

这是第一个正在工作的简单工具.该函数采用数据框并按指定的列和值进行过滤.

Here is the first easy one which is working. Function which takes a dataframe and filters by a specified column and value.

foo <- function(df, y, t = 4){
  tmp <- df %>% 
          filter(!!enquo(y) > t)
  ggplot(tmp, aes_(substitute(y))) + 
      geom_histogram()  
}
foo(mtcars, cyl)

现在我正尝试直接通过管道传输到ggplot函数...出现错误

Now I'm trying to pipe directly to the ggplot function...gives an error

foo <- function(df, y, t=4){
  df %>% 
     filter(!!enquo(y) > t) %>% 
        ggplot(aes_(substitute(y))) + 
            geom_histogram()  
}
foo(mtcars, cyl)

FUN(X [[i]]，...)中的错误:找不到对象'cyl' 另外:警告消息: 在FUN(X [[i]]，...)中:重新开始中断的承诺评估

Error in FUN(X[[i]], ...) : object 'cyl' not found In addition: Warning message: In FUN(X[[i]], ...) : restarting interrupted promise evaluation

和最后一个.如何添加构面?

and the last one. How to add a facet?

foo <- function(df, y, gr, t=4){
  df %>% 
       filter(!!enquo(y) > t) %>% 
  ggplot(aes_(substitute(y))) + 
      geom_histogram() +  
      facet_grid(~gr)
}
foo(mtcars, y= cyl, gr= vs)

编辑

第二个问题可以使用aes_q代替aes_& substitute. 来源

Edit

The second issue can be solved using aes_q instead of aes_ & substitute. Source

foo <- function(df, y, gr, t=4){
  y <- enquo(y)
  df %>% 
    filter(!!y > t) %>% 
       ggplot(aes_q(y)) + 
           geom_histogram()
}
foo(mtcars, cyl)

使用ggplot2_2.2.1