# Tutorial¶

NDlib is built upon networkx and is designed to configure, simulate and visualize diffusion experiments.

## Installation¶

In order to install the latest version of the library (with visualization facilities) use

pip install ndlib


## Chose a Diffusion model¶

Let’s start importing the required libraries

import networkx as nx
import ndlib.models.epidemics.SIRModel as sir


Once imported the selected model, SIR, and the networkx library we can initialize the simulation:

# Network Definition
g = nx.erdos_renyi_graph(1000, 0.1)

# Model Selection
model = sir.SIRModel(g)


## Configure the simulation¶

Each model has its own parameters: in order to completely instantiate the simulation we need to specify them using a Configuration object:

import ndlib.models.ModelConfig as mc

# Model Configuration
config = mc.Configuration()
model.set_initial_status(config)


The model configuration allows to specify model parameters (as in this scenario) as well as nodes’ and edges’ ones (e.g. individual thresholds).

Moreover it allows to specify the initial percentage of infected nodes using the percentage_infected model parameter.

It is also possible to explicitly specify an initial set of infected nodes: see ModelConfig for the complete set of use cases.

## Execute the simulation¶

In order to execute the simulation one, or more, iterations must be required using the model.iteration() and/or model.iteration_bunch(n_iterations) methods.

# Simulation
iterations = model.iteration_bunch(200)
trends = model.build_trends(iterations)


## Visualize the results¶

At the end of the simulation the diffusion trend can be visualized as follows (for matplotlib change ndlib.viz.bokeh in ndlib.viz.mpl)

from bokeh.io import output_notebook, show
from ndlib.viz.bokeh.DiffusionTrend import DiffusionTrend

viz = DiffusionTrend(model, trends)
p = viz.plot(width=400, height=400)
show(p)


Furthermore, a prevalence plot is also made available.

The prevalence plot captures the variation (delta) of nodes for each status in consecutive iterations.

from ndlib.viz.bokeh.DiffusionPrevalence import DiffusionPrevalence

viz2 = DiffusionPrevalence(model, trends)
p2 = viz2.plot(width=400, height=400)
show(p2)


Multiple plots can be combined in a multiplot to provide a complete description of the diffusive process

from ndlib.viz.bokeh.MultiPlot import MultiPlot
vm = MultiPlot()
m = vm.plot()
show(m)


Multiplots - implemented only for the bokeh provider - are also useful to compare different diffusion models applied to the same graph (as well as a same model instantiated with different parameters)

import ndlib.models.epidemics.SISModel as sis
import ndlib.models.epidemics.SIModel as si
import ndlib.models.epidemics.ThresholdModel as th

vm = MultiPlot()

# SIS
sis_model = sis.SISModel(g)
config = mc.Configuration()
sis_model.set_initial_status(config)
iterations = sis_model.iteration_bunch(200)
trends = model.build_trends(iterations)

viz = DiffusionTrend(sis_model, trends)
p3 = viz.plot(width=400, height=400)

# SI
si_model = si.SIModel(g)
config = mc.Configuration()
si_model.set_initial_status(config)
iterations = si_model.iteration_bunch(200)
trends = model.build_trends(iterations)

viz = DiffusionTrend(si_model, trends)
p4 = viz.plot(width=400, height=400)

# Threshold
th_model = th.ThresholdModel(g)
config = mc.Configuration()

# Set individual node threshold
threshold = 0.40
for n in g.nodes():