i am using mxgraph to show the process. I need to select a edge programtically. The mxgraph provids selectEdges(true,false,false) which will select all the edges in the graph. But i need to select a particular edge in the graph.
Suppose if there is vertex1, vertex2 and vertex3. Each of these vertex is connected using edges. I need to select the edge between vertex2 and vertex3. Whether mxgraph provides any api to dod so? Please help me.
The mxGraph class hold a mxGraphSelectionModel instance, which is where you perform most of the selection operations. clear() and addCell(Object) will give you the result you require.
You should use GraphComponent.
Use graphComponent.getCellAt(x,y) ( x y are you mouse/click coordinates)
when you get the returned object, make sure it is an edge by checking the boolean isEdge().
So if you have the x, y programatically you can use the same process I described.
For example u can get the common edge of two vertices and it would be your edge.
Related
I am trying to port code from python NetworkX to R igraph. In NetworkX there is a function with the name has_path that finds if two vertices have a path. I want to find in an efficient way all the vertices of a graph that don't have an edge between them but they have a path.
I think you can use the code below to check if there is a path from vertex V1 to V2 (the graph can be directed or undirected)
c(!is.infinite(distances(g, V1, V2, mode = "out")))
If you need to check this repeatedly in an undirected graph, simply break it into connected components and check if both vertices are within the same component. This will be very efficient, as the components need to be found only once.
See the components function. It gives you a membership vector. You need to check if the position corresponding to the two vertices has the same value (same component index).
If the graph is directed, the simplest solution is the one posted by #ThomasIsCoding. This is perfectly fine for a one-time check. Speeding up repeated checks is more trouble and warrants its own question.
I am trying to take a single layer of polygon buffers and delete the areas in which these circular buffers overlap (or intersect... I am not sure about the correct terminology here). I have so far tried the Intersection tool and Symmetrical difference tool, but these requires two layer inputs, and I am just working with a single layer. How can I accomplish this? I am working in QGIS.
Here is what I am working with:
I simply want to select and delete the areas where these circles overlap. I have searched this extensively online, but cannot find a solution that works for me, since I am only working with one layer.
you can try select by location analysis, if select "Where the feature" condition "Overlap", it select just overlap features.enter image description here
And delete after.
You can perform SQL Query with Execute SQL tool [
https://docs.qgis.org/3.16/en/docs/user_manual/processing_algs/qgis/vectorgeneral.html#id85]
Where Additional input datasources is your circle layer, that must have unique value, in my example attribute is called fid
Query is:
select c1.fid as fid1, c2.fid as fid2, intersection(c1.geometry,c2.geometry) as geometry
from input1 as c1, input1 as c2
where c1.fid > c2.fid and st_intersects(c1.geometry,c2.geometry)
query result is intersaction between geometries:
aftert that you can do symmetrical difference to optain
There is a new QGis plugin named "Buffer Without Overlaps" that works fine!
I've been trying to find a way to replicate the following network graph format in R using DiagrammeR/GraphViz, but without success (ignore the thick black arrow on N1): https://i.stack.imgur.com/oHpQz.png
The graph is a directed graph and each edge in a certain direction either ends with an arrowhead (-->) if the edge value is positive, or a circle/odot (--o) if the edge value is negative. Between a pair of nodes (ex. N1 -- A1), there can be an edge N1 --> A1 and an edge A1 --o N1, and these need to be concentrated so that the two edges look like one line with an arrowhead on one end and a circlehead on the opposite end (like this: o--->). These cannot be parallel or look like two edges ideally.
Another requirement is that the nodes have to be in very specific positions and remain there throughout model simulations where edges might change. From what I have tried and the documentation I have read, this is not possible to do in DOT format, but is possible in neato format.
This is where I get a problem. In neato, I can align the nodes exactly where I want them by defining their x,y positions. However, when I use concentrate = true to create the o---> edge from two otherwise parallel edges, only one type of arrowhead remains. So an edge that's supposed to look like o---> ends up looking like ---> or o---.
This is not a problem in DOT format as concentrate = true does what I want it to do, but in DOT I cannot assign exact node positions. I have tried getting around this using node ranks but without much luck. It seems to stack nodes I want in different ranks within the same rank. As well, concentrate = true doesn't seem to work for edges between nodes within the same rank, as it leaves them as two separate curved edges ---> and o--- without concentrating them.
The reason why I need this to work is because I'm running model simulations where the edges change, and I need to generate hundreds of such graphs. For easy comparison, the nodes need to stay in the same place for consistency.
This is the closest I could come up with using neato format (nodes are positioned the way I want but it's not showing the proper o---> for all the black edges minus self-edges; red edges are true one-way links): https://i.stack.imgur.com/YJBY7.jpg
If only the edges showed up as the proper o---> format, this would be perfect for my needs. If you know of any way to fix this issue using DiagrammeR/GraphViz, or even another program, I would be so grateful. Thanks!
You probably don't need concentrate. Look at arrowtail and dir (https://www.graphviz.org/doc/info/attrs.html#d:arrowtail and https://www.graphviz.org/doc/info/attrs.html#d:dir) and neato -n
digraph c {
graph[label="can neato do the work?"]
node[shape=circle]
a [pos="100,100"]
b [pos="200,100"]
c [pos="300,100"]
a->b [dir=both arrowtail=odot]
c->c [dir=both arrowtail=odot arrowhead=none]
}
Giving:
Given a set of vertices (say, for simplicity, that I start with one: G.V().hasId("something")), I want to obtain all outgoing edges and their target vertices. I know that .out() will give me all target vertices, but without the information about the edges (which have properties on them, too). On the other hand, .outE() will give me the edges but not the target vertices. Can I obtain both in a single Gremlin query?
Gremlin is as much about transforming graph data as it is navigating graph data. Typically folks seem to understand the navigation first which got you to:
g.V().hasId("something").outE()
You then need to transform those edges into the result you want - one that includes the edge data and it's adjacent vertex. One way to do that is with project():
g.V().hasId("something").outE()
project('e','v').
by().
by(inV())
Each by()-modulator supplied to project() aligns to the keys supplied as arguments. The first applies to "e" and the second to "v". The first by() is empty and is effectively by(identity()) which returns the same argument given to it (i.e. the current edge in the stream).
Never mind. Figured this out.
G.V().hasId("something").outE().as("E").otherV().as("V").select("E", "V")
I have a graph database in Azure CosmoDB that stores how similar vertices are and the edge contains the numeric value of how similar they are.
The complication is that I want to add an edge or update by incrementing the similarity value. This is the current code I have for adding:
g.V('A').addE('similar').to(g.V('B')).property('x', 10)
I need something that will increase X if the edge exists, or create it if not. Pseudo code exemplifying it:
g.V('A').updateE('similar').to(g.V('B')).property('x', currentValue+2).ifNulll({g.V('A').addE('similar').to(g.V('B')).property('x', 10)})
is there an easy way to achieve this ?
There is a known recipe for checking existence by using the pattern fold().coalesce(unfold()...) for vertex and similar pattern for edge. In your case, you want to update a property value as well.
Assuming there are vertices with IDs A and B, and edge goes from A-->B, the query might look like this:
g.withSack(0).V('B').as('toV').V('A').coalesce(
outE('similar').where(inV().as('toV')),
addE('similar').to('toV').property('similarity', 0)
)
.sack(assign).by('similarity').sack(sum).by(constant(2))
.property('similarity', sack())
Explanation:
Get B (target) vertex and save reference, get A (source) vertex.
Using coalesce, check if there is an edge connecting them, otherwise create such edge and set similarity to 0.
Assign the 'similarity' value to the sack, and sum the additional value.
Last, store the new value on the edge property.
Another query without using sack:
g.V('B').as('toV').V('A').coalesce(
outE('similar').where(inV().as('toV')),
addE('similar').to('toV').property('similarity', 0)
).property('similarity', values('similarity').fold(10, sum))