import scipy as sp
import numpy as np
a=sp.sparse.coo_matrix(np.random.randint(0,9,[4,5]))
b=sp.sparse.coo_matrix(np.random.randint(0,9,[4,2]))
sp.hstack([a,b]).toarray()
is giving me
AttributeError: 'numpy.ndarray' object has no attribute 'toarray'
could you help me with my silly mistake here?
sp.hstack (i.e. numpy.hstack) is the ordinary, dense hstack, which won't combine the sparse arrays correctly. It builds a 1D numpy array already (of object dtype; in other words, it just wraps the Python-level objects and crams them in there.) You want scipy.sparse.hstack:
In [332]: sp.hstack([a, b])
Out[332]:
array([<4x5 sparse matrix of type '<class 'numpy.int64'>'
with 17 stored elements in COOrdinate format>,
<4x2 sparse matrix of type '<class 'numpy.int64'>'
with 7 stored elements in COOrdinate format>], dtype=object)
In [333]: sp.hstack([a, b]).toarray()
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-333-4f469eb98b12> in <module>()
----> 1 sp.hstack([a, b]).toarray()
AttributeError: 'numpy.ndarray' object has no attribute 'toarray'
In [334]: sp.sparse.hstack([a, b])
Out[334]:
<4x7 sparse matrix of type '<class 'numpy.int64'>'
with 24 stored elements in COOrdinate format>
In [335]: sp.sparse.hstack([a, b]).toarray()
Out[335]:
array([[3, 2, 7, 0, 5, 5, 1],
[7, 1, 2, 1, 7, 0, 8],
[6, 1, 6, 1, 8, 6, 2],
[7, 6, 0, 5, 0, 8, 8]], dtype=int64)
