[PYTHON] Even beginners can do it! An easy way to write a Sankey Diagram on Plotly

What is SankyDiagram

The Sankey diagram (English Sankey diagram) is a diagram that expresses the flow rate between processes. The thickness of the arrow indicates the amount of flow. In particular, it is used to represent the displacement of energy, supplies, expenses, etc. Source: [Wikipedia](https://en.wikipedia.org/wiki/%E3%82%B5%E3%83%B3%E3%82%AD%E3%83%BC_%E3%83%80%E3 % 82% A4% E3% 82% A2% E3% 82% B0% E3% 83% A9% E3% 83% A0)

Benefits of implementing with plotly (Plotly Express)

• Can read data frames.
• Easy to write code.
• Interactive graph so users can move

Implementation of Sankey Diagram on Plotly

import pandas as pd
import plotly.express as px

#DF generation
#Create a data frame so that one row of data represents a transition
df =pd.DataFrame([['Cat1', 'CatA-2', 'AI', 'Normal'],
                  ['Cat1', 'CatA-3', 'AI', 'Normal'],
                  ['Cat1', 'CatA-3', 'No', 'NG'],
                  ['Cat3', 'CatA-3', 'Random', 'Normal'],
                  ['Cat3', 'CatA-5', 'Random', 'NG'],
                  ['Cat3', 'CatA-1', 'Random', 'NG'],
                  ['Cat3', 'CatA-1', 'No', 'NG']],
                columns=['one','two','three',"output"])

#Categorical variables as dummy variables
#Error if the last column of the data frame is a string?
df["output"] = pd.get_dummies(df["output"])

fig = px.parallel_categories(df, 
                             dimensions=['one','two','three','output'],
                             color="output",
                             color_continuous_scale=px.colors.diverging.BrBG,
                             labels={'one':'FirstArea', 'two':'SecondArea', 'three':'ThirdArea','output':'output'}
                            )
fig.show()