Lacij is a graph visualization library for Clojure with automatic layouts, edition and undo/redo support.
Latest commit ee9b7dc May 21, 2016


Lacij is a graph visualization library written in Clojure. It allows the display and the dynamic modification of graphs as SVG documents that can be viewed with a Web browser or with a Swing component. Undo/redo is supported for the dynamic modification. Automatic layout is provided for the visualization.


An online presentation of Lacij, dated from June 2011, can be found here:


The easiest way to use Lacij in your own projects is via Leiningen. Add the following dependency to your project.clj file:

Clojars Project


Example 1: creating a simple graph and exporting it as SVG.

(let [g (-> (graph :width 400 :height 400)
              (add-node :hermes "Hermes" :x 10 :y 30)
              (add-node :zeus "Zeus" :x 200 :y 125)
              (add-node :ares "Ares" :x 200 :y 225)
              (add-edge :father1 :hermes :zeus)
              (add-edge :father2 :ares :zeus)
    (export g "/tmp/simple.svg" :indent "yes"))

Simple graph

Example 2: using SVG styles to customize nodes and edges

(-> (graph :width 800 :height 400)
    (add-default-node-style :fill "lightgreen")
    (add-default-edge-style :stroke "royalblue")
    (add-node :hermes "Hermes" :x 10 :y 30 :style {:fill "lightblue"})
    (add-node :zeus "Zeus" :x 300 :y 150 :rx 15 :ry 15)
    (add-node :ares "Ares" :x 300 :y 250 :style {:fill "lavender" :stroke "red"})
    (add-edge :father1 :hermes :zeus "son of"
                :style {:stroke "darkcyan" :stroke-dasharray "9, 5"})
    (add-edge :father2 :ares :zeus)
    (add-default-node-attrs :rx 5 :ry 5)
    (add-node :epaphus "Epaphus" :x 450 :y 250)
    (add-edge :epaphus-zeus :epaphus :zeus)
    (add-node :perseus "Perseus" :x 600 :y 150)
    (add-edge :perseus-zeus :perseus :zeus)
    (add-label :father2 "son of" :style {:stroke "crimson"
                                         :font-size "20px"
                                         :font-style "italic"})
    (export "/tmp/styles.svg"))

Graph with styles

Example 3: automatic layout

Radial Layout:

Radial layout

Hierarchical Layout: Hierarchical layout

Learning by doing

All examples are available in the examples directory.

You can run the examples with the following command:

lein run -m <namespace-of-the-example>

For example:

lein run -m lacij.examples.undoredo


If you want to contribute and help this project, you can implement a layout algorithm of your choice.

See for some references.

Work in progress



Copyright (C) 2010-2013 Fraunhofer Gesellschaft

Distributed under the Eclipse Public License, the same as Clojure.