I want to draw a network which can show the weight of each edge.
Currently, I was able to draw an unweighted graph using PUNGraph of SNAP.
G = snap.PUNGraph.New()
However, I wasn't able to find the class for the weighted graph.
I don't want to just put the value above the edge, I want to somehow resize the edge base on the value of the edges.
Could someone tell me how I can draw graph something like below?
If possible I would like a solution using SNAP.
I end up using nodeXL which is capable of drawing a graph likes below.
Also D3.js supports a lot of good representing features.
I am still looking for more fascinating tools.
Related
I'm trying to write a little graph visualizer in P5js but I can't find a simple(-ish) algorithm to follow.
I've found ways to do it with D3 and I've found some dense textbook snippets (like this) but I'm looking for something in between the two.
Can someone explain the simplest algorithm for drawing a graph (force-directed or otherwise) or point me to a good resource?
Thanks for your help!
I literally just started something similar.
It's fairly easy to code, you just need to think about the 3 separate forces acting on each node, add them together and divide that by the mass of the node to get the movement of each node.
Gravity, put a simple force acting towards the centre of the canvas so the nodes dont launch themselves out of frame
Node-Node replusion, You can either use coulombs force (which describes particle-particle repulsion) or use the gravitational attraction equation and just reverse it
Connection Forces, this ones a little tricky, define a connection as 2 nodes and the distance between them. when the actual distance between them is different from the defined distance, add a force in the direction of the connection multiplied by the difference between the defined and the actual distance
I have to create the nodes and edges, having interconnections. I am using d3 js for the same. Now the problem is that the graphs look so much messy. I tried using quadratic bezier curves to draw the edges between the nodes. I want that If a press a button it should rearrange into simplified view.
I happened to look at metacademy, they are a open source project. Which have the exact functionality I am looking for. https://metacademy.org/graphs/edit/new, you would need to login. However not able to find their part of code which is doing the same.
Initially created graph
After pressing the refresh button
I am pretty new to d3js, so I will be thankful for any help/suggestions.
I see this is a pretty old question, but FWIW, I designed the graph you're referring to.
Getting graphs to organize so that it minimizes edge crossing is an area of active research. For metacademy, I integrated d3.js + dagre
https://github.com/dagrejs/dagre
I drew a small planar graph with Graphviz but in one place there's an intersection of two edges. I read on SO that not all planar graphs can be drawn without intersections because it's an NP-hard problem. I also read that there aren't even implemented complex algorithms in Graphviz that do that. But that intersection is as easy to fix as possible so there probably is a way to get rid of it.
Here are the options I used:
overlap = false;
splines = curved;
nodesep = 0.5;
And here's the graph:
So, is there a way of fixing that one intersection (25-38 with 7-18) without changing the order of edges like I did here? Isn't there like at least O(n^2) algorithm that would swap two vertices and check if the intersection disappeared?
This is kind of a hotfix:
Add an invisible edge between nodes 7 and 25, ie 7 -- 25 [style="invis"];. This clause may be added to the end of the graph definition so it shouldn't interfere with any automatic generation.
It feels like cheating, however, at least the order of the payload edges in the graph definition file remains untouched.
I cannot give an explanation of why this works,unfortunately. In particular, adding edges between other nodes incident to the offending edges does not produce the desired result.
Graphviz version: 2.38.0 (20140413.2041)
I came across following graph layout proposed in the paper NodeTrix :
The big blocks that are visible are nodes themselves (A sort of composite node of a sub-graph).
I see that the edges are some sort of curves which seem to not intersect too much among themselves. Also, the nodes and edges don't intersect among themselves. Paper doen't talk about it btw.
I was hoping to implement this visualization. I have following doubts:
Q1. Is this some specific algorithm to arrange Nodes-Edges so that the graph look good, as shown in this paper ? Any other algorithm in general ?
Q2. Is there some special algorithm for the curved edges shown above as well ?
It would be great if someone could figure out the exact algorithm in the above figure visually, but some general similar algorithm should also do.
One algorithm is Force-directed graph drawing. It will produce an output very different from the posted picture, but it is quite popular and might give you a place to start looking.
To be honest, I suspect that the shown graph is manually laid out.
EDIT: Answer to comment
In the example all nodes are square boxes, and the edges start/end diagonal to the sides of the boxes. A way to to this could be
Place boxes using force-direction (or likely some customized version of it, forces depend on the size of the box)
Imagine a "guide-edge" going directly between the centers of the boxes
Calculate the the places where the guide-edge intersects the boxes, and use that as the start/end points of the real, drawn edge.
Make the real edge start diagonal to the sides, and use bezier curves to draw the curve.
You probably want to represent this as some vector format, that has bezier cures built in, e.g., svg.
Are there any algorithms to minimize edge crossings in a graph? For example if I have a transition matrix of the graph.
I found methods like trying to place the nodes around the other node, but I'd like to know some other ideas.
There's a range of well established algorithms/libraries that have been developed for graph drawing applications, you can get a bit of background here.
To draw undirected graphs a popular choice is the force-based layout algorithm, in which graph edges are treated as springs (attractive forces) while the vertices are treated like charged particles (applying repulsive forces). The algorithm works by updating the vertex positions based on these forces until a steady-state is reached. You can read more about force based methods here. Since these algorithms search for an equilibrium solution they often result in pseudo-optimal layouts, without much edge tangling.
You might be interested in making use of one of the many graph drawing libraries that are available. The Graphviz package is generally pretty good and supports a number of different algorithms for different graph drawing applications.