# annoy.

The nearest neighbor problem is very common in data science. It's useful in recommender situations but also with neural embeddings in general. It's an expensive thing to calculate so it is common to calculate approximate distances as a proxy. In python a very likeable tool for this is annoy.

**Episode Notes**

The code below should be more accurate than before.

```
annoy = AnnoyIndex(columns, 'euclidean')
for i in range(vecs.shape[0]):
annoy.add_item(i, vecs[i, :])
# this is the line that we changed from 1 -> 10
annoy.build(n_trees=10)
plt.figure(figsize=(5, 5))
plt.scatter(vecs[:, 0], vecs[:, 1], s=1);
indices = annoy.get_nns_by_vector(np.array([-1., -1.]), 2000)
subset = vecs[indices, :]
# this should now show a proper circle
plt.scatter(subset[:, 0], subset[:, 1], s=1);
```

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