DiagrammeR is a package in R that is used to create graphs and flowcharts using Graphviz and Mermaid. This can be useful for displaying data. In this article, we’ll cover how to create graphs using the grViz() in the DiagrammeR package, including:

  1. What is DiagrammeR?
  2. What is grViz()in DiagrammeR?
  3. How to create nodes, edges, labels and their substitution and connection using grViz().
  4. How to render the plot graph with Knit to HTML.

What Is DiagrammeR?

DiagrammeR is a package within htmlwidgets for R. It’s used to generate graphs using Graphviz and Mermaid library.

 

How to Install DiagrammeR

In order to install DiagrammeR to create plot graphs, there are two steps. First, you’ll create an R Markdown document, which will set the output to HTML. Then, you’ll install the DiagrammeR package. Here’s how:

 

1. Create an R Markdown document.

In RStudio → Go to File → New File →R Markdown. Then, give the title and select the output format as HTML.

R markdown create a new document screenshot.
R Markdown create a new document screenshot. | Screenshot: Indhumathy Chelliah

The R Markdown document will have the title and other information at the top.

R Markdown document page screenshot with HTML output.
R Markdown document page screenshot with HTML output. | Screenshot: Indhumathy Chelliah

Below that we will have R chunks which have delimiters ```{r} and ```.

When you render the R Markdown document, it will run each chunk and embed the results beneath the code chunk or you can run each code chunk and the result will be displayed for that code chunk.

We can knit the R Markdown document to HTML output.

 

2. Install the DiagrammeR Package

Go to Packages → Install on the right side of the RStudio and enter the package name DiagrammeR and click “Install.”

Diagrammer installation screen screenshot.
Diagrammer installation screen screenshot. | Screenshot: Indhumathy Chelliah

And that’s it, you’ve installed DiagrammeR.

A tutorial on what is and how to use DiagrammeR. | Video: Jupyter Lectures

More on RThe Ultimate Guide to Relational Operators in R

 

How to Create a Graph in DiagrammeR

DiagrammeR package uses the grViz() function for Graphviz graphs. Let’s see how to use grViz() function to create graphs. While creating a graph, we have to mention the layout, node attributes, edge attributes and connection. In the graph below, green color circles are called nodes. A=15, B=10, etc. are the labels of the nodes.

The -> arrow mark is known as the edges. Here’s how to set the node, edge attributes, label and substitutions and connections required to create it.

Flow chart with two paths coming out of one node.
Flow chart made with DiagrammeR and grViz(). | Image: Indhumathy Chelliah

5 Steps to Creating a Graph in DiagrammeR With grViz()

  1. Set the layout.
  2. Enter the node attributes.
  3. Enter the edge attributes.
  4. Enter the label and substitutions.
  5. Enter the connection details.

 

1. Set the Layout

The default layout is the dot.

layout = dot

 

2. Enter the Node Attributes

Include the node shape, color, style and width, etc. that you want for your graph.

node [shape = circle,color=green,style=filled,fixedsize=True,width=0.6]

 

3. Enter the Edge Attributes

Detail your edge attributes. These include color, arrowhead, arrow tail, pen width and direction, etc.

edge[color=grey,arrowhead=vee]

 

4. Enter the Label and Substitutions

We have to include the label and substitution for the node.

A[label = 'A= @@1']
B[label = 'B=@@2']
C[label = 'C=@@3']
D[label = 'D=@@4']
E[label = 'E=@@5']

@@1 -> is the substitution. 

[1]:15
[2]:10
[3]:20
[4]:2
[5]:2

Here, 1 is the footnote number. The value 15 will be substituted in place of 1 when the graph is rendered.

 

5. Enter the Connection Details

In my graph A is connected to B and C. B is connected to D and C is connected to E.

A->B
A->C
B->D
C->E

 

Full R Code and Graph

```{r , echo=FALSE}
library(DiagrammeR)
grViz("
  digraph {
  layout = dot
    node [shape = circle,color=green,style=filled,fixedsize=True,width=0.6]
    edge[color=grey,arrowhead=vee]
    A[label = 'A= @@1']
    B[label = 'B=@@2']
    C[label = 'C=@@3']
    D[label = 'D=@@4']
    E[label = 'E=@@5']
    A->B
    A->C
    B->D
    C->E
    
  }
  [1]:15
  [2]:10
  [3]:20
  [4]:2
  [5]:2
   ")
flow chart graph with one node s;it into two paths
Output for the full R code. | Image: Indhumathy Chelliah

 

Creating a Plot Graph Using DiagrammeR Example 

Let’s create another graph where nodes A and C are in the same rank and B, and E are in the same rank.

If we mention rank=same {A->C}, A and C nodes will be placed in the same line.

rank=same {A->C}

rank=same {B->E}

 

Full Code and Graph

```{r , echo=FALSE}
library(DiagrammeR)
grViz("
  digraph {
  layout = dot
    node [shape = circle,color=green,style=filled,fixedsize=True]
    edge[color=grey,arrowhead=vee,minlen = 1]
    A[label = 'A=@@1']
    B[label = 'B=@@2']
    C[label = 'C=@@3']
    D[label = 'D=@@4']
    E[label = 'E=@@5']
    A->B
    B->D
    edge [minlen = 2]
    rank=same {A->C}
    rank=same {B->E}
    
  }
  [1]:15
  [2]:10
  [3]:20
  [4]:2
  [5]:2
   ")
Flow graph with multiple paths coming from each node.
Output of the R code. | Image: Indhumathy Chelliah

 

How to Add a Node to Your Plot Graph in DiagrammeR

Let’s create a node from the down arrow of another node.

flow chart with nodes coming in between arrows.
Creating nodes from the down arrow. | Image: Indhumathy Chelliah

Here’s how to create the graph mentioned above.

 

1. Create a Blank Node

First, we have to create a blank node.

A -> blank1;
blank1 -> B[minlen=10];
  {{ rank = same; blank1 B }}
blank1 -> C

C -> blank2;
blank2 -> D[minlen=1];
  {{ rank = same; blank2 E }}
blank2 -> E [minlen=10]
Flow graph with blank nodes.
Blank nodes added along the down arrows. | Image: Indhumathy Chelliah

 

2. Create a blank Node Label

After that we can make the blank node label = “ “ and the width and height to be very small (0.01).

blank1[label = '', width = 0.01, height = 0.01]
blank2[label = '', width = 0.01, height = 0.01]

 

Full Code and Graph

```{r , echo=FALSE}
library(DiagrammeR)
grViz("
  digraph {
  layout = dot
    node [shape = circle,color=green,style=filled,fontsize=45,fixedsize=True,width=4.0]
    edge[color=grey,arrowhead=vee,penwidth=5,arrowsize=5]
    A[label = 'A= @@1']
    B[label = 'B=@@2']
    C[label = 'C=@@3']
    D[label = 'D=@@4']
    E[label = 'E=@@5']
    
blank1[label = '', width = 0.01, height = 0.01]    
A -> blank1;
blank1 -> B[minlen=10];
  {{ rank = same; blank1 B }}
blank1 -> C

blank2[label = '', width = 0.01, height = 0.01] 
C -> blank2;
blank2 -> D[minlen=1];
  {{ rank = same; blank2 E }}
blank2 -> E [minlen=10]
    
  }
  [1]:15
  [2]:10
  [3]:20
  [4]:2
  [5]:2
   ")
```
Removing the blank nodes from the chart.
Removing the blank nodes. | Image: Indhumathy Chelliah

 

3. Remove the Arrow Mark

The next step is to remove the arrow mark. It can be removed by mentioning the edge attribute dir=none.

A -> blank1[dir=none];
C -> blank2[dir=none];

 

Full Code and Graph

```{r , echo=FALSE}
library(DiagrammeR)
grViz("
  digraph {
  layout = dot
    node [shape = circle,color=green,style=filled,fontsize=45,fixedsize=True,width=4.0]
    edge[color=grey,arrowhead=vee,penwidth=5,arrowsize=5]
    A[label = 'A= @@1']
    B[label = 'B=@@2']
    C[label = 'C=@@3']
    D[label = 'D=@@4']
    E[label = 'E=@@5']
    
    
blank1[label = '', width = 0.01, height = 0.01]   
A -> blank1[dir=none];
blank1 -> B[minlen=10];
  {{ rank = same; blank1 B }}
blank1 -> C

blank2[label = '', width = 0.01, height = 0.01]   
C -> blank2[dir=none];
blank2 -> D[minlen=1];
  {{ rank = same; blank2 E }}
blank2 -> E [minlen=10]
    
  }
  [1]:15
  [2]:10
  [3]:20
  [4]:2
  [5]:2
   ")
```
node flow chart without extra arrows along the pathways.
Removing the extra arrows from the graph. | Image: Indhumathy Chelliah

 

How to Render Your Plot Graph in DiagrammeR With Knit to HTML

Select the option knit -> knit to html.

Kint to HTML screenshot
Screenshot of knit to HTML. | Screenshot: Indhumathy Chelliah

The whole R Markdown document will be rendered into an HTML document.

If you don’t want the r-code to be displayed in the HTML output, mention echo =False in the r-chunk code.

```{r , echo=FALSE}```

More on Data SciencePython Data Visualization With Seaborn & Matplotlib

 

Advantages to Using DiagrammeR to Create Plot Graphs

DiagrammeR is a package in R that allows the creation of graphs using Graphviz and mermaid styles. In this article, we have covered using Graphviz style. We have covered how to create nodes, labels, edges, connections and layouts for the graphs using the grViz() function in the DiagrammeR package. We have also covered node attributes, edge attributes, labels and their substitutions. We have covered only the dot layout, which is the default layout in this article.

Expert Contributors

Built In’s expert contributor network publishes thoughtful, solutions-oriented stories written by innovative tech professionals. It is the tech industry’s definitive destination for sharing compelling, first-person accounts of problem-solving on the road to innovation.

Learn More

Great Companies Need Great People. That's Where We Come In.

Recruit With Us