How to use the command 'fdp' (with examples)

The ‘fdp’ command is part of Graphviz, a suite of tools used to render sophisticated graphical representations of structural information as attributed diagrams. Specifically, ‘fdp’ is a command-line tool used to create force-directed layouts of network graphs, which is particularly useful for visualizing complex relationships or hierarchies in data. It offers a set of layouts such as ‘dot,’ ’neato,’ ’twopi,’ ‘circo,’ ‘fdp,’ ‘sfdp,’ ‘osage,’ and ‘patchwork,’ allowing for versatile and dynamic graphical output formats like PNG, SVG, JPEG, and more.

Use case 1: Render a PNG image with a filename based on the input filename and output format

Code:

fdp -T png -O path/to/input.gv

Motivation:

A common task in data visualization involves converting graph descriptions into images. By automatically naming the output file based on the input, users can ensure consistency and organization, which is crucial when processing many files or when integrating graph rendering into larger automated workflows.

Explanation:

• -T png: Specifies that the output format should be PNG, a common image format supported by most applications and browsers.
• -O: Tells ‘fdp’ to automatically derive the output filename from the input graph file’s name, appending the appropriate extension (.png in this case).

Example Output:

This command takes an input file ‘input.gv’ and produces an image such as ‘input.gv.png’. It visualizes the graph stored in ‘input.gv’ using a force-directed layout, helpful for analyzing network data patterns.

Use case 2: Render a SVG image with the specified output filename

Code:

fdp -T svg -o path/to/image.svg path/to/input.gv

Motivation:

In cases where the output file needs a specific name, perhaps to match a naming convention or for version control purposes, specifying the filename gives users greater control over their file organization and output management.

Explanation:

• -T svg: Selects SVG as the output format, which is beneficial for web use due to its scale-independent nature.
• -o path/to/image.svg: Directs the output file to a specific path with a defined filename, ensuring easy retrieval and usage.
• path/to/input.gv: The path to the input file containing graph description written in the DOT language.

Example Output:

This command generates an SVG file at ‘path/to/image.svg’ that visualizes the described relationships from the ‘input.gv’ file.

Use case 3: Render the output in a specific format

Code:

fdp -T ps|pdf|svg|fig|png|gif|jpg|json|dot -O path/to/input.gv

Motivation:

Different projects may require various file formats depending on the medium where the graph will be used. Whether for print (PDF, PS) or web (SVG, PNG), having the flexibility to choose the precise output format directly in the command line aids in adapting to diverse documentations and presentations.

Explanation:

• -T ps|pdf|svg|fig|png|gif|jpg|json|dot: The -T option followed by a format tells ‘fdp’ to render the graph in one of the specified formats, each serving different purposes (e.g., graph interchange with JSON or editing with DOT).
• -O: Automatically creates the output filename based on the input graph’s filename.

Example Output:

Using this general command allows one to quickly convert a graph into formats like ‘input.gv.pdf’ or ‘input.gv.jpg’, depending on the business requirements or technical restrictions.

Use case 4: Render a gif image using stdin and stdout

Code:

echo "digraph {this -> that} " | fdp -T gif > path/to/image.gif

Motivation:

Directly piping graph data via standard input to generate visualizations is powerful for quick tests, scripts, or systems where the graph is generated dynamically or fetched online. This method is efficient for quick iterations without creating intermediate files.

Explanation:

• echo "digraph {this -> that} ": Uses echo to create a simple graph specification directly in shell, demonstrating on-the-fly graph creation.
• | fdp -T gif: Pipes the input specification directly to ‘fdp’ that generates a GIF image format.
• > path/to/image.gif: Redirects the output to a file named ‘image.gif’, storing the resultant visualized graph.

Example Output:

The simple graph defined (a digraph with one edge ’this’ to ’that’) is rendered as ‘image.gif’, which can be viewed using any GIF-supported application.

Use case 5: Display help

Code:

fdp -?

Motivation:

Accessing the help or manual of a command is essential for understanding the full breadth of its capabilities, especially for advanced users who wish to leverage ‘fdp’ to its fullest potential. This is ideal for quick on-the-spot reference or learning about new or less-used options.

Explanation:

• -?: Invokes the help command, which outputs a brief manual on how to use every feature and option available with the ‘fdp’ tool.

Example Output:

Running this command provides a comprehensive list of all options and descriptions, helping users to learn and utilize ‘fdp’ effectively.

Conclusion:

The ‘fdp’ command from Graphviz is an indispensable tool for translating graph descriptions into visually appealing layouts. By offering a range of output options and formats, it accommodates diverse requirements from detailed print-ready documents to lively web graphics. Whether naming files automatically, using custom names, or dynamically generating graphs from streams, ‘fdp’ gives users the tools to enhance and showcase their data effectively.