Video and Slides

Watch the talk on Loom at Clojure/West 2014 and view slides. Also, there's a video of the talk at LispNYC and slides.

Usage

Leiningen/Clojars [group-id/name version]

Namespaces

loom.graph   - records & constructors
loom.alg     - algorithms (see also loom.alg-generic)
loom.gen     - graph generators
loom.attr    - graph attributes
loom.label   - graph labels
loom.io      - read, write, and view graphs in external formats
loom.derived - derive graphs from existing graphs using maps and filters

Documentation

API Reference

Frequently Asked Questions

Feel free to join Loom mailing list and ask any questions you may have.

Basics

Create a graph:

;; Initialize with any of: edges, adacency lists, nodes, other graphs
(def g (graph [1 2] [2 3] {3 [4] 5 [6 7]} 7 8 9))
(def dg (digraph g))
(def wg (weighted-graph {:a {:b 10 :c 20} :c {:d 30} :e {:b 5 :d 5}}))
(def wdg (weighted-digraph [:a :b 10] [:a :c 20] [:c :d 30] [:d :b 10]))
(def rwg (gen-rand (weighted-graph) 10 20 :max-weight 100))
(def fg (fly-graph :successors range :weight (constantly 77)))

If you have GraphViz installed, and its binaries are in the path, you can view graphs with loom.io/view:

(view wdg) ;opens image in default image viewer

Inspect:

(nodes g)
=> #{1 2 3 4 5 6 7 8 9}

(edges wdg)
=> ([:a :c] [:a :b] [:c :d] [:d :b])

(successors g 3)
=> #{2 4}

(predecessors wdg :b)
=> #{:a :d}

(out-degree g 3)
=> 2

(in-degree wdg :b)
=> 2

(weight wg :a :c)
=> 20

(map (juxt graph? directed? weighted?) [g wdg])
=> ([true false false] [true true true])

Add/remove items (graphs are immutable, of course, so these return new graphs):

(add-nodes g "foobar" {:name "baz"} [1 2 3])

(add-edges g [10 11] ["foobar" {:name "baz"}])

(add-edges wg [:e :f 40] [:f :g 50]) ;weighted edges

(remove-nodes g 1 2 3)

(remove-edges g [1 2] [2 3])

(subgraph g [5 6 7])

Traverse a graph:

(bf-traverse g) ;lazy
=> (9 8 5 6 7 1 2 3 4)

(bf-traverse g 1)
=> (1 2 3 4)

(pre-traverse wdg) ;lazy
=> (:a :b :c :d)

(post-traverse wdg) ;not lazy
=> (:b :d :c :a)

(topsort wdg)
=> (:a :c :d :b)

Pathfinding:

(bf-path g 1 4)
=> (1 2 3 4)

(bf-path-bi g 1 4) ;bidirectional, parallel
=> (1 2 3 4)

(dijkstra-path wg :a :d)
=> (:a :b :e :d)

(dijkstra-path-dist wg :a :d)
=> [(:a :b :e :d) 20]

Other stuff:

(connected-components g)
=> [[1 2 3 4] [5 6 7] [8] [9]]

(bf-span wg :a)
=> {:c [:d], :b [:e], :a [:b :c]}

(pre-span wg :a)
=> {:a [:b], :b [:e], :e [:d], :d [:c]}

(dijkstra-span wg :a)
=> {:a {:b 10, :c 20}, :b {:e 15}, :e {:d 20}}

Attributes on nodes and edges:

(def attr-graph (-> g
                (add-attr 1 :label "node 1")
                (add-attr 4 :label "node 4")
                (add-attr-to-nodes :parity "even" [2 4])
                (add-attr-to-edges :label "edge from node 5" [[5 6] [5 7]])))

; Return attribute value on node 1 with key :label
(attr attr-graph 1 :label)
=> "node 1"

; Return attribute value on node 2 with key :parity
(attr attr-graph 2 :parity)
=> "even"

; Getting an attribute that doesn't exist returns nil
(attr attr-graph 3 :label)
=> nil

; Return all attributes for node 4
; Two attributes found
(attrs attr-graph 4)
=> {:parity "even", :label "node 4"}

; Return attribute value for edge between nodes 5 and 6 with key :label
(attr attr-graph 5 6 :label)
=> "edge from node 5"

; Return all attributes for edge between nodes 5 and 7
(attrs attr-graph 5 7)
=> {:label "edge from node 5"}

; Getting an attribute that doesn't exist returns nil
(attrs attr-graph 3 4)
=> nil

; Remove the attribute of node 4 with key :label
(def attr-graph (remove-attr attr-graph 4 :label))

; Return all attributes for node 4
; One attribute found because the other has been removed
(attrs attr-graph 4)
=> {:parity "even"}

Derived graphs:

; Build a derived graph using a node mapping
(nodes (mapped-by #(+ 10 %) g))
=> #{11 12 13 14 15 16 17 18 19}

; Subgraphs of g
(edges (nodes-filtered-by #{1 2 3 5} dg))
=> ([1 2] [2 1] [2 3] [3 2])

(edges (subgraph-reachable-from dg 1))
=> ([1 2] [2 1] [2 3] [3 2] [3 4] [4 3])

Dependencies

Nothing but Clojure. There is optional support for visualization via GrapViz.

TODO

See Loom TODO board.

Testing

lein test-all

Contributors

Names in no particular order:

• Justin Kramer
• [Aysylu Greenberg] (https://github.com/aysylu), aysylu [dot] greenberg [at] gmail [dot] com, @aysylu22
• Robert Lachlan, robertlachlan@gmail.com
• Stephen Kockentiedt

Namespaces

The dependency graph of Loom's namespaces, generated by lein-ns-dep-graph.

License

Copyright (C) 2010-2016 Aysylu Greenberg & Justin Kramer (jkkramer@gmail.com)

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