# Tag: matrix

## Why is ‘scipy.sparse.linalg.spilu’ less efficient than ‘scipy.linalg.lu’ for sparse matrix?

I posted this question on https://scicomp.stackexchange.com, but received no attention. As long as I get answer in one of them, I will inform in the other. I have a matrix B which is sparse and try to utilize a function scipy.sparse.linalg.spilu specialized for sparse matrix to factorize B. Could you please explain why this function […]

## Create a matrix with np.random.normal

I need to create an nxn matrix in which the numbers in the cells are distributed following a Gaussian distribution. This code may not go well because it fills a cell with a sequence. how can I do? Answer Edited for border of zeros np.random.normal takes a size keyword argument. You can use it like […]

## How to update the 1st value of the sub list with another list

I want to add the 1st element of each sublist with the values of another list Output (comming): Output (want): Answer Here let me tell you what is happening in your code… In this line you made a nested list in which all the sublists are pointing to the same sublist in memory. In this […]

## Delete values over the diagonal in a matrix with python

I have the next problem with a matrix in python and numpy given this matrix Cmpd1 Cmpd2 Cmpd3 Cmpd4 Cmpd1 1 0.32 0.77 0.45 Cmpd2 0.32 1 0.14 0.73 Cmpd3 0.77 0.14 …

## Python-Scipy sparse Matrices – what is A[i, j] doing?

According to my previous question here (Python – Multiply sparse matrix row with non-sparse vector by index) direct indexing of sparse matrices is not possible (at least not if you don’t want to work with the three arrays by which the sparse.csr matrix is defined, data, indices, indptr). But I just found out, that given […]

## Appending matrix A with matrix B

Say I have two matrices A and B. For example, A = numpy.zeros((5,5)) B = np.eye(5) Is there a way to append A and B?

## Pandas dataframe.dot division method

I am trying to divide two series of different length to return the matrix product dataframe of them. I can multiply them using the dot method (from this answer): I’ve tried the div method, but this just fills the dataframe with NaNs: Likewise the standard division operator also returns the same result: So I’m a bit stumped as to what

## Difference between numpy.array shape (R, 1) and (R,)

In numpy, some of the operations return in shape (R, 1) but some return (R,). This will make matrix multiplication more tedious since explicit reshape is required. For example, given a matrix M, if we …

## How can I find the dimensions of a matrix in Python?

How can I find the dimensions of a matrix in Python. Len(A) returns only one variable. Edit: Is (I assume) generating a matrix of integers (less likely strings). I need to find the size of that matrix, so I can run some tests without having to iterate through all of the elements. As far as the data type goes, I

## Pretty print 2D Python list

Is there a simple, built-in way to print a 2D Python list as a 2D matrix? So this: [[“A”, “B”], [“C”, “D”]] would become something like A B C D I found the pprint module, but it doesn’t …