holes.py

# Example from README
from topologylayer.nn import AlphaLayer, BarcodePolyFeature
import torch, numpy as np, matplotlib.pyplot as plt

# random pointcloud
np.random.seed(0)
data = np.random.rand(100, 2)

# optimization to increase size of holes
layer = AlphaLayer(maxdim=1)
x = torch.autograd.Variable(torch.tensor(data).type(torch.float), requires_grad=True)
f1 = BarcodePolyFeature(1,2,0)
optimizer = torch.optim.Adam([x], lr=1e-2)
for i in range(100):
    optimizer.zero_grad()
    loss = -f1(layer(x))
    loss.backward()
    optimizer.step()

# save figure
y = x.detach().numpy()
fig, ax = plt.subplots(ncols=2, figsize=(10,5))
ax[0].scatter(data[:,0], data[:,1])
ax[0].set_title("Before")
ax[1].scatter(y[:,0], y[:,1])
ax[1].set_title("After")
for i in range(2):
    ax[i].set_yticklabels([])
    ax[i].set_xticklabels([])
    ax[i].tick_params(bottom=False, left=False)
plt.savefig('holes.png')