A lightweight Racket module which draws a graph of nodes and edges in a circular layout, as an alternative to more powerful graph-rendering e.g. graphviz.
Nodes are defined using make-cl-node (which sets a name, size, a label and color), and edges are defined using make-cl-edge (which defines the source and target nodes, the weight of the edge, a label, and whether the edge is directed, i.e. has an arrow). A list of these nodes and edges are passed to draw-circular-layout along with a destination drawing context (dc<%>); scale factor and center of the graph is also specified.
#lang racket
(require circular-layout)
(require racket/gui/base)
;; a simple graph with 5 nodes and some edges
(definenodes (list
(clnode "a"23"a (23)""white")
(clnode "b"17"b (17)""red")
(clnode "c"11"c (11)""lightblue")
(clnode "d"15"d (15)""green")
(clnode "e"10"e (10)""violet")))
(defineedges (list
(cledge "a""a"1"10"#t) (cledge "a""b"1"5"#t) (cledge "a""c"1"3"#t) (cledge "a""d"1"5"#t) (cledge "b""a"1"7"#t)
(cledge "b""c"1"5"#t) (cledge "b""b"1"5"#t)
(cledge "c""c"1"5"#t) (cledge "c""b"1"3"#t) (cledge "c""d"1"3"#t) (cledge "d""d"1"5"#t) (cledge "d""a"1"5"#t) (cledge "d""e"1"5"#t)
(cledge "e""e"1"5"#t) (cledge "e""d"1"5"#t)))
;; set up a drawing canvas with a bitmap, and an image-snip% to display in REPL
(definetarget (make-bitmap 400400))
(definedc (new bitmap-dc% [bitmap target]))
(make-object image-snip% target)
;; call the circular-layout function to draw the graph
(draw-circular-layout #:dc dc #:nodes nodes #:edges edges #:center '(200 . 200) #:scale 10)