1Here is an example of an
---
1 | 1
2 | 0
3 | 1
incidence matrix
with 4 edges and 4 nodes. Remember, the columns are the edges and rows are the nodes themselves.
1 2 3 4Below is a JavaScript implementation of the same thing. ```js var incMat = [ [0, 1, 1, 1], [1, 1, 0, 0], [1, 0, 0, 1], [0, 0, 1, 0] ]; ``` To make a directed graph, use
--------
1 | 0 1 1 1
2 | 1 1 0 0
3 | 1 0 0 1
4 | 0 0 1 0
-1
for an edge leaving a particular node and 1
for an edge entering a node.
```js
var incMatDirected = [
[ 0, -1, 1, -1],
[-1, 1, 0, 0],
[ 1, 0, 0, 1],
[ 0, 0, -1, 0]
];
```
Graphs can also have weights on their edges. So far, we have unweighted edges where just the presence and lack of edge is binary (0
or 1
). You can have different weights depending on your application. A different weight is represented as numbers greater than 1.
incMatUndirected
should only contain five nodes.
testString: assert((incMatUndirected.length === 5) && incMatUndirected.map(function(x) { return x.length === 4 }).reduce(function(a, b) { return a && b }) , 'incMatUndirected
should only contain five nodes.');
- text: There should be a first edge between the first and second node.
testString: assert((incMatUndirected[0][0] === 1) && (incMatUndirected[1][0] === 1), 'There should be a first edge between the first and second node.');
- text: There should be a second edge between the second and third node.
testString: assert((incMatUndirected[1][1] === 1) && (incMatUndirected[2][1] === 1), 'There should be a second edge between the second and third node.');
- text: There should be a third edge between the third and fifth node.
testString: assert((incMatUndirected[2][2] === 1) && (incMatUndirected[4][2] === 1), 'There should be a third edge between the third and fifth node.');
- text: There should be a fourth edge between the second and fourth node.
testString: assert((incMatUndirected[1][3] === 1) && (incMatUndirected[3][3] === 1), 'There should be a fourth edge between the second and fourth node.');
```