A new csr object is constructed in each call :-(Īs a hack (though scipy is relatively stable these days), you can do the dot product directly on the sparse data: timeit numpy.dot(x_csr.data, x_csr.data) Transposition is very cheap, but there is no efficient C implementation of csr * csc (in the latest scipy 0.9.0). With 49757 stored elements in Compressed Sparse Row format> Now x_csr and x_dok are 50% sparse: print repr(x_csr) X = ((n) * 2).astype(int).astype(float) # 50% sparse vector if you call transpose(copy=False)), just like with numpy arrays.ĮDIT: some timings via ipython: import numpy, scipy.sparse These use efficient, C implementations under the hood (including multiplication), and transposition is a no-op (esp. Here we discuss the uses of MATLAB, what is 3 D Matrix? and how to create 3D arrays in MATLAB and also some manipulations on them.Use a scipy.sparse format that is row or column based: csc_matrix and csr_matrix. The output that we will get will have rows and columns interchanged as follows: i.e., changing rows with columns or vice versa. We can use this function if we want to rearrange the dimensions of the matrics.
The same thing is then done for 2nd page 2. This will create a 2D matrix with 6 rows and 5 columns:Īs you can notice, RESHAPE will work column-wise, so first all the elements of A take along the column, for the first page. This is useful mainly during visualization of dataįor Example: Create a 6*5 matrics using two 3*5 matrices MATLAB provides us with a couple of functions to manipulate the elements of a multidimensional array. Now, access = A(2,3,1) will give us 0 as output Functions to manipulate the elements of a Multidimensional Array To demonstrate this, let’s use the 3D matrix A which we used above, So, 2,3,1 element of a 3D Matrix will be the element present at 2nd row, 3rd column of the 1st page To do this simply use subscripts as integers. How can we access the elements of the array? So to extend our above example, we will simply give,ī(:,:,4) = and output will be: Now, if we need to further expand this array, we can simply give the elements of 4th array that we need to add:
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