The documentation says, "No more than p levels of the dendrogram tree are displayed. A “level” includes all nodes with p merges from the last merge." (p is another parameter) I can't figure out what "p merges from the last merge" means. Can anyone explain it?
(I've created dendrograms of the same data with truncate_mode='level' and truncate_mode='lastp'; I didn't find the comparison illuminating.)
The following code demonstrates truncate_mode='level' and truncate_mode='lastp':
from scipy.cluster import hierarchy
import matplotlib.pyplot as plt
import numpy as np
np.random.seed(1729)
ytdist = np.random.randint(1, 1000, 36)
Z = hierarchy.linkage(ytdist, 'single')
fig, ax_rows = plt.subplots(ncols=6, nrows=2, sharey=True, figsize=(16, 5))
for ax_row, truncate_mode in zip(ax_rows, ['level', 'lastp']):
hierarchy.dendrogram(Z, ax=ax_row[0])
ax_row[0].set_title('default, no truncation')
for ind, ax in enumerate(ax_row[1:]):
if truncate_mode == 'level':
p = len(ax_row) - ind - 1
else:
p = len(ax_row) - ind
hierarchy.dendrogram(Z, truncate_mode=truncate_mode, p=p, ax=ax)
ax.set_title(f"truncate_mode='{truncate_mode}', p={p}")
plt.tight_layout()
plt.show()
