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 Python Data Type Q&A » numpy » sparse

### 1. Fastest way to convert a Numpy array into a sparse dictionary?    stackoverflow.com

I'm interested in converting a numpy array into a sparse dictionary as quickly as possible. Let me elaborate: Given the array:

``````numpy.array([12,0,0,0,3,0,0,1])
``````
I wish to produce the dictionary:
``````{0:12, 4:3, 7:1}
``````
As you can see, we ...

### 2. Scipy sparse... arrays?    stackoverflow.com

So, I'm doing some Kmeans classification using numpy arrays that are quite sparse-- lots and lots of zeroes. I figured that I'd use scipy's 'sparse' package to reduce the storage ...

### 3. Adding a numpy array to a scipy.sparse.dok_matrix    stackoverflow.com

I have a `scipy.sparse.dok_matrix` (dimensions m x n), wanting to add a flat numpy-array with length m.

``````for col in xrange(n):
dense_array = ...
dok_matrix[:,col] = ...``````

### 4. How to elementwise-multiply a scipy.sparse matrix by a broadcasted dense 1d array?    stackoverflow.com

Suppose I have a 2d sparse array. In my real usecase both the number of rows and columns are much bigger (say 20000 and 50000) hence it cannot fit in memory ...

### 5. how to do linear interpolation on a 2D numpy array having sparse data?    stackoverflow.com

I have a 2D numpy array... there are some values in the image and rest is sparse. For linear imterpolation, I want to take the first column of the array. See ...

### 6. Matrix multiplication for sparse matrices in Python    stackoverflow.com

I want to multiply a sparse matrix A, with a matrix B which has 0, -1, or 1 as elements. To reduce the complexity of the matrix multiplication, I can ignore ...

### 7. sparse 3d matrix/array in Python?    stackoverflow.com

In scipy, we can construct a sparse matrix using scipy.sparse.lil_matrix() etc. But the matrix is in 2d. I am wondering if there is an existing data structure for sparse 3d matrix / ...

### 8. How to transform numpy.matrix or array to scipy sparse matrix    stackoverflow.com

For Scipy sparse matrix, one can use todense() or toarray() to transform to Numpy.matrix or array. What are the functions to do the inverse? I searched, but got no idea what keywords ...