html - html の visnetwork からのグラフのレイアウトが小さすぎるのはなぜですか

Question

以下の example-Rmd をレンダリングすると、次のようになります (Chrome では、実際には Firefox との違いはありません)。

図が小さすぎて、必要な「実際の」グラフを見ると、高さが小さすぎて、高さと幅の比率がさらに悪くなります。

再現可能な例を次に示します。

---
title: "Untitled"
author: "author"
date: "9 Mai 2018"
output: html_document
---

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

## Example

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```{r echo=FALSE}
require(visNetwork, quietly = TRUE)
# minimal example
nodes <- data.frame(id = 1:20)
edges <- data.frame(from = sample(c(1:20), 10), to = sample(c(1:20), 10))
visNetwork(nodes, edges, width = "100%", height = "100%") %>%
                               visNodes() %>%
                               visOptions(highlightNearest = TRUE) %>%
                               visInteraction(navigationButtons = TRUE, 
                                              dragNodes = FALSE,
                                              dragView = FALSE, zoomView = FALSE) %>%
                               visEdges(arrows = 'to')
```

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