If you're starting with a single (1,N) scipy.csr_matrix and just want to go to an array you can also:
scipy_csr_matrix = csr_matrix((data, indices, indptr), shape=shape) sparse_tensor = pa.SparseCSRMatrix.from_scipy(scipy_csr_matrix) arr = pa.array(sparse_tensor.to_tensor().to_numpy()[0]) But that assumes 1-dimension and goes to dense representation. On Thu, Jul 7, 2022 at 1:27 AM David Li <lidav...@apache.org> wrote: > If I'm not mistaken, what you want is basically an extension type [1] for > tensors, so you can have a column where each row contains a tensor/matrix. > This has been discussed for quite some time [2]. > > Incidentally, you can keep the three-field representation but pack it into > a single toplevel field with the Struct type. > > [1]: https://arrow.apache.org/docs/python/extending_types.html > [2]: https://issues.apache.org/jira/browse/ARROW-1614 > > On Wed, Jul 6, 2022, at 19:01, dl via user wrote: > > I have tabular data with one record field of type scipy.sparse.csr_matrix. > I want to convert this tabular data to a pyarrow table. I had been first > converting the csr_matrix first to a custom representation using three > fields (shape, keys, indices) and building the pyarrow table using a schema > with the types of these fields and table data with a separate list for each > field (and each list having one entry per input record). I was hoping I > could use a single pyarrow.SparseCSRMatrix field instead of the custom > three field representation. Is that possible? Incidentally, the shape of > the csr_matrix is typically (1,N) where N may vary for different records. > But I don't think "typically (1,N)" matters. It would work with variable > shape (M,N). The shape field has type pyarrow.List with value_type = > pyarrow.int32(). > > > On 7/6/2022 2:53 PM, Rok Mihevc wrote: > > Hey David, > > I don't think Table is designed in a way that you could "populate" it with > a 2D tensor. It should rather be populated with a collection of equal > length arrays. > Sparse CSR tensor on the other hand is composed of three arrays (indices, > indptr, values) and you need a bit more involved logic to manipulate those > than regular arrays. See [1] for memory layout definition. > > What are you looking to accomplish? What access patterns are you expecting? > > Rok > > [1] https://github.com/apache/arrow/blob/master/format/SparseTensor.fbs > > On Wed, Jul 6, 2022 at 10:48 PM dl <dydx...@yahoo.com> wrote: > > Hi Rok, > > What data type would I use for a pyarrow SparseCSRMatrix in a schema? I > need to build a table with rows which include a field of this type. I don't > see a related example in the test module. I'm doing something like: > > schema = pyarrow.schema(fields, metadata=metadata) > table = pyarrow.Table.from_arrays(table_data, schema=schema) > > where fields is a list of tuples of the form (field_name, pyarrow_type), > e.g. ('field1', pyarrow.string()). What should pyarrow_type be for a > SparseCSRMatrix field? Or will this not work? > > Thanks, > David > > > > On 7/1/2022 9:18 AM, Rok Mihevc wrote: > > We lack pyarow sparse tensor documentation (PRs welcome), so tests are > perhaps most extensive description of what is doable: > https://github.com/apache/arrow/blob/master/python/pyarrow/tests/test_sparse_tensor.py > > Rok > > On Fri, Jul 1, 2022 at 5:38 PM dl via user <user@arrow.apache.org> wrote: > > So, I guess this is supported in 8.0.0. I can do this: > > *import *numpy *as *np*import *pyarrow *as *pa*from *scipy.sparse *import > *csr_matrix > > a = np.random.rand(100) > a[a < .9] = 0.0 > s = csr_matrix(a) > arrow_sparse_csr_matrix = pa.SparseCSRMatrix.from_scipy(s) > > Now, how do I use that to build a pyarrow table? Stay tuned... > > > On 7/1/2022 8:19 AM, dl wrote: > > I find pyarrow.SparseCSRMatrix mentioned here > <https://arrow.apache.org/docs/python/integration/extending.html?highlight=sparse#pyarrow.pyarrow_wrap_sparse_csr_matrix>. > But how do I use that? Is there documentation for that class? > > > On 7/1/2022 7:47 AM, dl wrote: > > > Hi, > > I'm trying to understand support for sparse tensors in Arrow. It looks > like there is "experimental" support using the C++ API > <https://arrow.apache.org/docs/cpp/api/tensor.html?highlight=sparse#sparse-tensors>. > When was this introduced? I see in the code base here > <https://github.com/apache/arrow/blob/master/python/pyarrow/tensor.pxi> > Cython sparse array classes. Can these be accessed using the Python API. > Are they included in the 8.0.0 release? Is there any other support for > sparse arrays/tensors in the Python API? Are there good examples for any of > this, in particular for using the 8.0.0 Python API to create sparse tensors? > > Thanks, > David > > > >
