Python (scipy): resizing a sparse matrix

Question

I have a problem resizing the matrix - the set_shape function seems to have no effect:

 >>> M <14x3562 sparse matrix of type '<type 'numpy.float32'>' with 6136 stored elements in LInked List format> >>> new_shape = (15,3562) >>> M.set_shape(new_shape) >>> M <14x3562 sparse matrix of type '<type 'numpy.float32'>' with 6136 stored elements in LInked List format> 

Anyone else come across this?

I also tried to do this manually, i.e.

 >>> M._shape = new_shape >>> M.data = np.concatenate(M.data, np.empty((0,0), dtype=np.float32)) 

but this causes an error:

 *** TypeError: only length-1 arrays can be converted to Python scalars 

or

 >>> M.data = np.concatenate(M.data, []) *** TypeError: an integer is required 

For reference:

• Python 2.6.5 (r265: 79063, Apr 16, 2010 1:57:41 PM)
• scipy 0.11.0.dev-03f9e4a

Answer 1

If you just want to add a string of zeros to the end:

 >>> M = sp.lil_matrix((14, 3562)) >>> sp.vstack([M, sp.lil_matrix((1, 3562))]) <15x3562 sparse matrix of type '<type 'numpy.float64'>' with 0 stored elements in COOrdinate format>