plotly-sankey | Examples using Plotly to build Sankey Diagrams | Data Visualization library

This problem looks really strange, but only until you will analyze how the sankey plot in plotly is created:

When you create the sankey plot, you send to it:

1. Nodes list
2. Links list

These lists are bounded with each other. When you create the 5-length node list, any edge will know about 0,1,2,3,4 in its starts and ends. In your program, you creates node wrongly - you create the list of links and then go through it and create nodes. Look at your diagram. It has two black nodes with undefined inside. And what is the length of your dataset... Yes, 5. Your node indices ends on 4 and no target nodes are really defined. You add the sixth list in your dataset and - bingo! - there are nodes[5] exists! Just try to add another new line in your dataset:

[1,7,1,'#FF0000','WAKA','rgba(219, 233, 246,0.5)']

And you will see that another black bar is colored to red. You have five nodes (because you have 5 links and you create node by iterating for links list), but links target indices are 5,6,7. You can fix it with two ways:

1. Change Target's in your dataset to 2,3,4
2. Create nodes and links separately (right way)

I hope I helped you in your problem and in plot creation understanding (what is more important IMO).

Edit: Here is the example of separate nodes/links creation (note that node part in data_trace uses only nodes_df data, link part in data_trace uses only links_df data and nodes_df and links_df length are not equal):