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Tree-plots in Python

How to make interactive tree-plot in Python with Plotly. An examples of a tree-plot in Plotly.

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Basic Tree-Plot in Plotly with igraph

In [3]:
import plotly.plotly as py
import plotly.graph_objs as go

import igraph
from igraph import *
igraph.__version__
Out[3]:
'0.7.1'

Set Up Tree with igraph

In [4]:
nr_vertices = 25
v_label = map(str, range(nr_vertices))
G = Graph.Tree(nr_vertices, 2) # 2 stands for children number
lay = G.layout('rt')

position = {k: lay[k] for k in range(nr_vertices)}
Y = [lay[k][1] for k in range(nr_vertices)]
M = max(Y)

es = EdgeSeq(G) # sequence of edges
E = [e.tuple for e in G.es] # list of edges

L = len(position)
Xn = [position[k][0] for k in range(L)]
Yn = [2*M-position[k][1] for k in range(L)]
Xe = []
Ye = []
for edge in E:
    Xe+=[position[edge[0]][0],position[edge[1]][0], None]
    Ye+=[2*M-position[edge[0]][1],2*M-position[edge[1]][1], None] 

labels = v_label

Create Plotly Traces

In [5]:
lines = go.Scatter(x=Xe,
                   y=Ye,
                   mode='lines',
                   line=dict(color='rgb(210,210,210)', width=1),
                   hoverinfo='none'
                   )
dots = go.Scatter(x=Xn,
                  y=Yn,
                  mode='markers',
                  name='',
                  marker=dict(symbol='dot',
                                size=18, 
                                color='#6175c1',    #'#DB4551', 
                                line=dict(color='rgb(50,50,50)', width=1)
                                ),
                  text=labels,
                  hoverinfo='text',
                  opacity=0.8
                  )

Create Text Inside the Circle via Annotations

In [6]:
def make_annotations(pos, text, font_size=10, font_color='rgb(250,250,250)'):
    L=len(pos)
    if len(text)!=L:
        raise ValueError('The lists pos and text must have the same len')
    annotations = go.Annotations()
    for k in range(L):
        annotations.append(
            go.Annotation(
                text=labels[k], # or replace labels with a different list for the text within the circle  
                x=pos[k][0], y=2*M-position[k][1],
                xref='x1', yref='y1',
                font=dict(color=font_color, size=font_size),
                showarrow=False)
        )
    return annotations  

Add Axis Specifications and Create the Layout

In [7]:
axis = dict(showline=False, # hide axis line, grid, ticklabels and  title
            zeroline=False,
            showgrid=False,
            showticklabels=False,
            )

layout = dict(title= 'Tree with Reingold-Tilford Layout',  
              annotations=make_annotations(position, v_label),
              font=dict(size=12),
              showlegend=False,
              xaxis=go.XAxis(axis),
              yaxis=go.YAxis(axis),          
              margin=dict(l=40, r=40, b=85, t=100),
              hovermode='closest',
              plot_bgcolor='rgb(248,248,248)'          
              )

Plot!

In [8]:
data=go.Data([lines, dots])
fig=dict(data=data, layout=layout)
fig['layout'].update(annotations=make_annotations(position, v_label))
py.iplot(fig, filename='Tree-Reingold-Tilf')
Out[8]:

Reference

See https://plot.ly/python/reference/ for more information and chart attribute options and http://igraph.org/python/ for more information about the igraph package!

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