英文:

R: using curly braces referring to column name within a conditionally-defined expression inside custom function does not work

问题

我已经定义了一个函数，该函数生成一个ggplot图表，其中y变量可以是级别或百分比，因此我已经包含了一个if-else来适当地修改选项。然后，我通过ggplotly运行图表以生成交互式版本，但悬停文本标签不按预期工作。如图所示，标签只是打印我的函数，而不是显示预期的y值。

我一直在寻找正确的方法，我认为我应该以某种方式使用eval，quote或expression，但不理解它们如何结合在一起。我知道的是，如果不使用例如quote，我会收到一个错误，提示对象values不存在，这表明函数的某部分在没有告知values是我的数据集中的列的情况下被评估。

这是我的reprex（示例代码）：

library(tidyverse) #for dplyr
library(ggplot2) #for chart
library(scales) #for axis label
library(plotly) #for interactive chart

# 数据集
dataset <- data.frame(geography_name=c("a","b","c","d","e","f"),
                      values=c(2,3,4,5,6,7))

# 自定义辅助函数
perc_form = function(x, d=1) sprintf(paste0("%1.",d,"f"), x) 

value_form = function(x,s=2,d= -1) format(signif(round(as.numeric(x), d),s), big.mark=",")

# 生成ggplot图表的函数
barchart <- function( data_set = dataset,
                      x_var = geography_name, 
                      y_var = values, 
                      bar_stat_type=NULL) {
  
  # 根据变量格式设置坐标轴类型
  if (bar_stat_type=="pct") {
    y_var_label <-  paste0("Rate: ",quote(perc_form({{y_var}})),"%")
    label_form <- (percent_format(accuracy=1))
  }  else if (bar_stat_type=="money") {
    y_var_label <- paste0("Level: £",quote(value_form({{y_var}})))
    label_form <- (comma_format())
  }
  
  # 图表
  barchart <- data_set %>%  
    ggplot(mapping = aes(x = {{x_var}}, 
                         y = {{y_var}}, 
                         text = paste0(geography_name, "\n",
                                       eval(y_var_label), "\n")))+
    geom_bar(stat = "identity", position = position_dodge(), width = 0.4)+
    scale_y_continuous(labels = eval(label_form)) #此评估有效
  
  return(barchart)
}

# 生成的ggplot图表正常
gg <- barchart(bar_stat_type="money")
gg

# ggplotly图表的悬停标签不正确
ggplotly(gg)

ggplotly标签不包括实际的y变量值

<details>
<summary>英文:</summary>

I have defined a function which produces a ggplot chart, where the y-variable can either be a level or a percentage, so I have included an if-else to amend the options appropriately. I then run the chart through ggplotly to produce an interactive version, but the hover-over text label does not work as intended. As shown in the picture, the label just prints my function instead of showing the y-value as intended.

I have struggled to find the right approach and think that I am supposed to use `eval`, `quote` or `expression` in some way, but don&#39;t understand how it all fits together. What I do know is that without using e.g. `quote`, I get an error saying the object `values` does not exist, which suggests that part of the function is evaluated without being told `values` is a column within my dataset. 

Here is my reprex:

library(tidyverse) #for dplyr
library(ggplot2) #for chart
library(scales) #for axis label
library(plotly) #for interactive chart

dataset

dataset <- data.frame(geography_name=c("a","b","c","d","e","f"),
values=c(2,3,4,5,6,7))

custom helper functions

perc_form = function(x, d=1) sprintf(paste0("%1.",d,"f"), x)

value_form = function(x,s=2,d= -1) format(signif(round(as.numeric(x), d),s), big.mark=",")

function producing ggplot chart

barchart <- function( data_set = dataset,
x_var = geography_name,
y_var = values,
bar_stat_type=NULL) {

Set axis type dependent on variable format

if (bar_stat_type=="pct") {
y_var_label <- paste0("Rate: ",quote(perc_form({{y_var}})),"%")
label_form <- (percent_format(accuracy=1))
} else if (bar_stat_type=="money") {
y_var_label <- paste0("Level: £",quote(value_form({{y_var}})))
label_form <- (comma_format())
}

Chart

barchart <- data_set %>%
ggplot(mapping = aes(x = {{x_var}},
y = {{y_var}},
text = paste0(geography_name, "\n",
eval(y_var_label), "\n")))+
geom_bar(stat = "identity", position = position_dodge(), width = 0.4)+
scale_y_continuous(labels = eval(label_form)) #this evaluation works

return(barchart)
}

ggplot chart is produced fine

gg <- barchart(bar_stat_type="money")
gg

ggplotly chart does not have correct hover-over labels

ggplotly(gg)

[ggplotly labels do not include actual y-variable value][1]


  [1]: https://i.stack.imgur.com/uXJvP.png

</details>


# 答案1
**得分**: 0

以下是代码部分的翻译：

```R
不需要使用 `quote` 或 `eval`。只需将您的 `y_var_label` 函数定义好，然后可以在 `ggplot2` 代码中调用它们：

```R
library(ggplot2)
library(scales)
library(plotly)

barchart <- function(data_set = dataset,
                     x_var = geography_name,
                     y_var = values,
                     bar_stat_type = NULL) {
  if (bar_stat_type == "pct") {
    y_var_label <- function(x) paste0("Rate: ", percent_format(x), "%")
    label_form <- percent_format(accuracy = 1)
  } else if (bar_stat_type == "money") {
    y_var_label <- function(x) paste0("Level: £", comma_format(x))
    label_form <- comma_format()
  }

  data_set %>%
    ggplot(mapping = aes(
      x = {{ x_var }},
      y = {{ y_var }},
      text = paste0(
        geography_name, "\n",
        y_var_label({{ y_var }}), "\n"
      )
    )) +
    geom_bar(stat = "identity", position = position_dodge(), width = 0.4) +
    scale_y_continuous(labels = label_form)
}

gg <- barchart(bar_stat_type = "money")

ggplotly(gg)

希望这对您有所帮助。如果有其他翻译或解释需求，请随时提问。

<details>
<summary>英文:</summary>

There is no need for `quote` or `eval`. Simply make you `y_var_label`s functions which can be called inside your `ggplot2` code:

library(ggplot2)
library(scales)
library(plotly)

barchart <- function(data_set = dataset,
x_var = geography_name,
y_var = values,
bar_stat_type = NULL) {
if (bar_stat_type == "pct") {
y_var_label <- function(x) paste0("Rate: ", perc_form(x), "%")
label_form <- percent_format(accuracy = 1)
} else if (bar_stat_type == "money") {
y_var_label <- function(x) paste0("Level: £", value_form(x))
label_form <- comma_format()
}

data_set %>%
ggplot(mapping = aes(
x = {{ x_var }},
y = {{ y_var }},
text = paste0(
geography_name, "\n",
y_var_label({{ y_var }}), "\n"
)
)) +
geom_bar(stat = "identity", position = position_dodge(), width = 0.4) +
scale_y_continuous(labels = label_form)
}

gg <- barchart(bar_stat_type = "money")

ggplotly(gg)

[![enter image description here][1]][1]


  [1]: https://i.stack.imgur.com/gn2i2.png

</details>