Add new plotly function sankey_from_2_df_cols()

[janosh]

Closes #26.

Examples

Random integers

import numpy as np
import pandas as pd

from pymatviz import sankey_from_2_df_cols

col_names = "col_a col_b".split()

df = pd.DataFrame(np.random.randint(1, 6, size=(100, 2)), columns=col_names)

fig = sankey_from_2_df_cols(df, col_names, labels_with_counts="percent")

]

from matminer.datasets import load_dataset

df_perov = load_dataset("matbench_perovskites")

# omitted lengthy code to calculate aflow and spglib spacegroups
# see examples/matbench_perovskites.ipynb
# ...

fig = sankey_from_2_df_cols(df_perov, ["spglib_spg_num", "aflow_spg_num"])

fig.update_layout(title="Matbench Perovskites Spglib vs Aflow Spacegroups")