在for循环中打印DiagrammeR对象

Question

有没有一种简单的方法可以从R Markdown文档中的循环中打印DiagrammeR对象？我有一个文档，其中为多个模型分别生成了一个回归表、一个图和一个图，并一起打印。使用for循环很容易做到这一点，但是DiagrammeR对象不会在循环内打印(即使使用像print(graph)这样的显式调用。

这在其他地方已经有了文档(参见：https://github.com/rich-iannone/DiagrammeR/issues/39 )，但2015年的建议解决方案现在似乎不起作用(并且仅限于html输出)。

参见下面的Rmd示例代码。

---
title: "DiagrammeR loop test"
author: ""
date: "11/20/2020"
output: pdf_document
---


# Some header
Printing a single flowchart works fine in knitr using the DiagrammeR package. 

```{r figure_1, out.width = "15%", echo = FALSE, fig.align = 'center', fig.cap = "Flowchart 1: This prints fine."}

DiagrammeR::grViz(“

  digraph test {

    node [shape = circle] 

      A; B

    A -> B

  }

    ")

Flowchart 2 which is inside a loop, however, does not print 


```{r figure_2, out.width = "15%", echo = FALSE, fig.align = 'center', fig.cap = "Flowchart 2: These two diagrams do not print even with an explicit print command."}

对于(1:2中的i){

graph <- DiagrammeR::grViz(“

  digraph test {

    node [shape = circle] 

      A; B

    A -> B

  }

    ")

打印(图形)

}

Answer 1

下面是如何修复它：

# Create an empty list to save the htmlwidgets
plot_list <- htmltools::tagList()

for (i in 1:2){
  
graph <- DiagrammeR::grViz(" 
      digraph test {

        node [shape = circle] 
          A; B

        A -> B

      }
        ")

# Store the htmlwidget inside this list
plot_list[[i]] <- graph 
}

#Print this list
plot_list