Question

尝试编写一个相对简单的包装器来生成一些图，但是无法确定如何指定整理评估指定为...的分组变量，这是一个面向变量但不通过分组区分的示例函数。

my_plot <- function(df = starwars,
                    select = c(height, mass),
                    ...){
    results <- list()
    ## Tidyeval arguments
    quo_select <- enquo(select)
    quo_group  <- quos(...)
    ## Filter, reshape and plot
    results$df <- df %>%
                  dplyr::filter(!is.na(!!!quo_group)) %>%
                  dplyr::select(!!quo_select, !!!quo_group) %>%
                  gather(key = variable, value = value, !!!quo_select) %>% 
                  ## Specify what to plot
                  ggplot(aes(value)) +
                  geom_histogram(stat = 'count')  +
                  facet_wrap(~variable, scales = 'free', strip.position = 'bottom')
    return(results)
}
## Plot height and mass as facets but colour histograms by hair_color
my_plot(df = starwars, select = c(height, mass), hair_color)

很棒，但是如何区分不同的hair_color？通常这是在aes()内完成的，但由于这是使用quos()的结果（即quo_group），我应该（我认为）使用aes_()代替

my_plot <- function(df = starwars,
                    select = c(height, mass),
                    ...){
    results <- list()
    ## Tidyeval arguments
    quo_select <- enquo(select)
    quo_group  <- quos(...)
    ## Filter, reshape and plot
    results$df <- df %>%
                  dplyr::filter(!is.na(!!!quo_group)) %>%
                  dplyr::select(!!quo_select, !!!quo_group) %>%
                  gather(key = variable, value = value, !!!quo_select) %>% 
                  ## Specify what to plot, including colouring by the supplied ... groupings
                  ggplot(aes_(~value, colour = !!!quo_group)) + 
                  geom_histogram(stat = 'count')  +
                  facet_wrap(~variable, scales = 'free', strip.position = 'bottom')
    return(results)
}
## Plot height and mass as facets but colour histograms by hair_color
my_plot(df = starwars, select = c(height, mass), hair_color)
Error in !quo_group : invalid argument type

在我出错的地方，我几次看不到或没看过Programming with dplyr。

任何人都可以指出我的错误/告诉我的方式吗？

Answer 1

新发布的ggplot2 v3.0.0在!!内部支持aes()。经过一些小的修改，您的功能现在可以正常工作

library(tidyverse)

my_plot <- function(df = starwars,
                    select = c(height, mass),
                    ...){
  results <- list()

  ## Tidyeval arguments
  quo_select <- enquo(select)

  # only need quo here, if quos is used then we need to `unlist` to 
  # convert its output from list to vector
  quo_group  <- quo(...) 

  ## Filter, reshape and plot
  results$df <- df %>%
    dplyr::filter(!is.na(!!!quo_group)) %>%
    dplyr::select(!!quo_select, !!!quo_group) %>%
    gather(key = variable, value = value, !!!quo_select) %>% 
    ## Specify what to plot, including coloring by the supplied dots `...` 
    ggplot(aes(value, color = !!quo_group, fill = !!quo_group)) +  # unquote inside aes
    geom_histogram(stat = 'count')  +
    facet_wrap(vars(variable), scales = 'free', strip.position = 'bottom')
  return(results)
}

## Plot height and mass as facets but color histograms by hair_color
my_plot(df = starwars, select = c(height, mass), hair_color)

由reprex package（v0.2.0.9000）于2018-09-12创建。

Answer 2

我不确定我理解这个问题。这是否满足要求？

library(ggplot2)
library(data.table)

your_plot <- function(df, select, color=NULL) {

  df <- as.data.table(df)[, mget(na.omit(c(select, color)))]

  ggplot(melt(df, color, select), aes_string(x=quote(value), color=color)) +
    geom_histogram(stat="count") +
    facet_wrap(~variable, scales="free", strip.position="bottom")

}

your_plot(dplyr::starwars, c("height", "mass"), "hair_color")

这使用melt来堆叠select变量，并为每个堆栈重复color个变量。它还使用aes_string，因为aes(x=value, color=color)时color=NULL失败。

整洁的评估编程和ggplot2

2 个答案: