Enhanced Appendices | An Enchantment of Digital Archaeology > Information Diffusion on a Network

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Information Diffusion on a Network

;; built for NetLogo version 6.04 ;; a version of the itineraries model that ;; loads a network dataset. ’Travel difficulty’ is represented by ;; the ‘strength’ value of the links, puts some agents on it, ;; has them wander around, at differing speeds (or distances) ;; and measures how long it takes for a message to be ‘heard’ by ;; everyone ;;---- ;; the model is built by combining default code snippets in ;; NetLogo: ;; network import ;; communication t-t network example ;; link walking turtles ;; Thanks to Andreas Angourakis for looking over the code and ;; suggesting improvements ;; in the interface, you’ll need to create a slider called ;; num-walkers ;; and make sure that the minimum is set to 2 and the ‘value’ (starting position of the slider) is at least 2 or more ;; you can also build some monitors. For instance, right-click in ;; the interface and select new monitor, then paste this code ;; into it: ;; ((count walkers with [message?]) / (count walkers)) * 100 ;; this will tell you the per cent of the population that has ;; heard the message. ;; you could graph this by making a new plot and giving it the ;; same code ;; right-click, select plot, and in plot update commands paste ;; the same code. breed [nodes node] ;; these are our sites nodes-own [node-id] breed [walkers walker] ;; the turtles who wander around walkers-own [ ;; variables that only the walkers own location message? new-location journey-time] links-own [strength] globals [links-list travel-factor] ;; travel factor has to be ;; accessible by turtles of either breed to setup import-network create-walkers num-walkers [ set color red set shape “person” set size 2 set location one-of nodes ;; tells our new walker its new ;; home move-to location ;; moves the walker there directly set message? false ;; ignorance is bliss set new-location one-of [link-neighbors] of location ;; gives ;; the walkers a travel goal set journey-time 1 ;; initial degree of forward movement: one ;; patch at a time ] ask one-of walkers [ set message? true ] reset-ticks end to go ;; we ask the walkers: ;; go walking, ;; talk to anyone else who happens to be present, ;; change their color if they’ve encountered someone with the message, ;; test to see if they’ve arrived at their new destination ;; and then if everyone has the message we stop the simulation. ask walkers [ move communicate recolor check-if-arrived ] if ((count walkers with [message?]) / (count walkers)) * 100 = 100 [stop] end to move face new-location ;; make sure they’re heading the correct ;; direction at all times ifelse random-fl oat 1 > 0.5 [fd 1][fd journey-time] ;; without the chance of them slowing down to one patch at a ;; time, they sometimes will overshoot the target and get caught ;; overshooting it back and forth. end to check-if-arrived let arrived one-of nodes-here ;; see if the node they’re at happens to be the one they’re ;; looking at if arrived = new-location [set location new-location choose-destination] ;; if it is ;; update their ‘location’ variable to where they are now ;; and search out a new destination end to choose-destination set new-location one-of [link-neighbors] of location ;; see what places are connected to this one ask one-of links with [ (end1 = [location] of myself and end2 = [new-location] of myself) or (end2 = [location] of myself and end1 = [new-location] of myself)] ;; adjust the travel-factor (distance, ease of travel) to the ;; value of the new path/link [set travel-factor strength] ;; adjust speed so that it is modulated by this new value set journey-time (1 / travel-factor) end to communicate ;; turtle procedure if any? other walkers-here with [message?] ;; hello? anybody here? [ set message? true ] ;; if yes, then now I know the message too end to recolor ;; walker procedure if message? [ set color blue ] end to import-network clear-all set-default-shape turtles “circle” import-attributes layout-circle (sort turtles) (max-pxcor – 1) import-links reset-ticks end ;; This procedure reads in a files that contains node-specific ;; attributes ;; including an unique identification number to import-attributes ;; This opens the file, so we can use it. file-open “attributes.txt” ;; Read in all the data in the file ;; data on the line is in this order: ;; node-id attribute1 attribute2 while [not file-at-end?] [ ;; this reads a single line into a three-item list let items read-from-string (word “[“ file-read-line “]”) create-nodes 1 [ ;; note the change set node-id item 0 items set size item 1 items set color item 2 items ] ] file-close end ;; This procedure reads in a file that contains all the links ;; The file is simply 3 columns separated by spaces. In this ;; example, the links are directed. The first column contains ;; the node-id of the node originating the link. The second ;; column the node-id of the node on the other end of the link. ;; The third column is the strength of the link. to import-links ;; This opens the file, so we can use it. file-open “links.txt” ;; Read in all the data in the file while [not file-at-end?] [ ;; this reads a single line into a three-item list let items read-from-string (word “[“ file-read-line “]”) ask get-node (item 0 items) [ create-link-with get-node (item 1 items) ;; nb! Create-link-with is undirected, create-link-to is ;; directed! [ set label item 2 items set strength item 2 items] ] ] file-close end ;; Helper procedure for looking up a node by node-id. to-report get-node [id] report one-of nodes with [node-id = id] end

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