Connections

Connections between the nodes is the most important part of nadi. you can load networks by loading a file or string. The network is a simple multiline text with one edge (input -> output) in each line. comments starting with # are supported.

Default is Empty Network

Tasks are run by default with an empty network. So you might still be able to work with network attributes, but the nodes will be empty. also note that when you load network it replaces the old one including the attributes.

network.someattr = 1234;
network.someattr

Results:

1234

But we can see the nodes are not there,

network count()
network nodes.NAME

Results:

0

[]

Trying to run node functions on the empty network means nothing is run

node render("{NAME}")

Results:

Loading Network from String

Here assume we have a network consisting of nodes of dams and gages like the following where dam nodes start with d and gages with g:

network load_str("
d1 -> d2
d3 -> g2
d2 -> g1
g1 -> d4
g2 -> d4
d4 -> g3
");
network svg_save(
   "./output/simple-count.svg",
	label="[{INDEX}] {_NAME}"
)

Results:

Loading Network from a File

we can load a network from a file:

network load_file("./data/mississippi.net");
network svg_save(
   "./output/ex-network-conn.svg",
	label="[{INDEX}] {_NAME}"
)

Results:

Modifying the network

You can modify the network after loading it as well. The example below extracts just the nodes that are dams. Compare this with the previous network to see how the connections are retained during the subsets.

network load_str("
d1 -> d2
d3 -> g2
d2 -> g1
g1 -> d4
g2 -> d4
d4 -> g3
");
node.is_dam = NAME match "^d[0-9]+";
network subset(nodes.is_dam);
network svg_save(
   "./output/simple-count-subset.svg",
	label="[{INDEX}] {_NAME}"
)

Results:

This can be useful when you want to remove nodes that do not satisfy some selection criteria for your analysis without having to redo the network detection part.