在具有向量值参数的非标准评估函数中使用`facet_wrap`

如何解决在具有向量值参数的非标准评估函数中使用`facet_wrap`

我想制作一个使用ggplot和facet_wrap的函数，并将函数变量传递给facet。

我可以使用带引号的参数执行以下操作。

library(tidyverse)

my_grid_plot <- function(facet_by){
  ggplot(mtcars,aes(wt,disp)) +
    geom_point() +
    facet_wrap(facet_by)
}

my_grid_plot(facet_by = 'am')  
my_grid_plot(facet_by = 'vs')  
my_grid_plot(facet_by = c('am','vs')) 

但是，我想使用不带引号的参数来做到这一点，例如

# does not work yet; this is what I want
my_grid_plot(facet_by = am)  
my_grid_plot(facet_by = vs)  
my_grid_plot(facet_by = c(am,vs))

我知道我可以将vars与facet_wrap一起使用，例如

ggplot(mtcars,disp)) +
  geom_point() +
  facet_wrap(vars(am,vs))

所以我可以做这样的事情

my_grid_plot2 <- function(facet_by){
  ggplot(mtcars,disp)) +
    geom_point() +
    facet_wrap(vars({{facet_by}}))
}

# works fine
my_grid_plot2(am)
my_grid_plot2(vs)

但是如果facet_by是向量，那将行不通。

# does not work; obscure error
my_grid_plot2(c(am,vs))

那么有没有一种方法可以得到我想要的东西，即facet_by采用名称向量的单个变量名吗？

解决方法

我不知道这是正确的方法还是最好的方法，而且似乎有些怪异，但我认为它可以完成工作。受https://stackoverflow.com/a/57709169/1009979

的启发

 Expanded(
                child: GridView(
                  physics: BouncingScrollPhysics(),gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(crossAxisCount: 2),children: [1,2,3,4,5,6,7,8,9,10,11,12]

                       // Wrap each item (Card) with Focused Menu Holder
                      .map((e) => FocusedMenuHolder(
                        menuWidth: MediaQuery.of(context).size.width*0.50,blurSize: 5.0,menuItemExtent: 45,menuBoxDecoration: BoxDecoration(color: Colors.grey,borderRadius: BorderRadius.all(Radius.circular(15.0))),duration: Duration(milliseconds: 100),animateMenuItems: true,blurBackgroundColor: Colors.black54,menuOffset: 10.0,// Offset value to show menuItem from the selected item
                        bottomOffsetHeight: 80.0,// Offset height to consider,for showing the menu item ( for example bottom navigation bar),so that the popup menu will be shown on top of selected item.
                        menuItems: <FocusedMenuItem>[
                          // Add Each FocusedMenuItem  for Menu Options
                          FocusedMenuItem(title: Text("Open"),trailingIcon: Icon(Icons.open_in_new),onPressed: (){
                            Navigator.push(context,MaterialPageRoute(builder: (context)=>ScreenTwo()));
                          }),FocusedMenuItem(title: Text("Share"),trailingIcon: Icon(Icons.share),onPressed: (){}),FocusedMenuItem(title: Text("Favorite"),trailingIcon: Icon(Icons.favorite_border),FocusedMenuItem(title: Text("Delete",style: TextStyle(color: Colors.redAccent),),trailingIcon: Icon(Icons.delete,color: Colors.redAccent,],onPressed: (){},child: Card(
                              child: Column(
                                children: <Widget>[
                                  Image.asset("assets/images/image_$e.jpg"),))
                      .toList(),

,

一种选择是让 tidyselect 完成繁重的工作：

my_grid_plot2 <- function(facet_by){
  by <- rlang::enexpr(facet_by) %>%
    tidyselect::eval_select(mtcars)

  ggplot(mtcars,aes(wt,disp)) +
    geom_point() +
    facet_wrap(names(by))
}

## All of the following now work as expected
my_grid_plot2(am)
my_grid_plot2(vs)
my_grid_plot2(c(am,vs))

my_grid_plot2('am')
my_grid_plot2('vs')
my_grid_plot2(c('am','vs'))