All Questions
3,952
questions
2
votes
1
answer
31
views
Lattice-boltzmann simulation runs over the object mask, simulating areas that should be just black
I'm trying to simulate a tesla valve using the method, starting from
this code.
The problem is that the mask, the boundaries, or the bounce-back are not being applied correctly.
If I reverse the ...
- 21
0
votes
1
answer
55
views
Efficient stochastic numerical integration over many trajectories
I am implementing a numerical method for solving stochastic differential equations using the Euler-Maruyama method.
What I have works, but it is not efficient. The reason is that because of the ...
- 173
0
votes
1
answer
30
views
My Python's Minesweeper function is returning different values when it should be constant values
I wrote a Minesweeper in Python using a class, the random and the Numpy modules. By choosing the difficulty, it sets up the dimension of the board and creates it, with the help of Numpy. It, then, ...
- 11
2
votes
1
answer
72
views
Optimize this Python code that involves matrix inversion
I have this line of code that involves a matrix inversion:
X = A @ B @ np.linalg.pinv(S)
A is an n by n matrix, B is an n by m matrix, and S is an m by m matrix. m is smaller than n but usually not ...
- 203
1
vote
2
answers
84
views
Rotating a vector field in an efficient way in python
I need to rotate a 3D vector field by 90 degrees. I do that by first using the NumPy function rot90 (see the docs here). Then I rotate each component at each position in a very inefficient way: using ...
- 1,929
1
vote
0
answers
53
views
Optimal function to scan numpy matrix
I have a binary 2D numpy array that represents transactions and items. For item I (represented as columns), I want to calculate the total number of transactions (represented as rows) that purchased ...
- 21
1
vote
1
answer
71
views
Creating Matrix from Vector Entries and Deprecation Warning from NumPy
I want to create a square matrix, let say 4X4, which the entries are taken from a vector, with length 16. This vector entry will be arranged in the column of matrix. Suppose that u is a vector with ...
- 35
-1
votes
1
answer
42
views
numpy.dot function and by-hand calculation
I am working on calculating pcov from a Jacobian matrix by hand, and understand most of it but am struggling to understand how the .dot function works from numpy in python. I have looked at the manual ...
- 35
1
vote
1
answer
70
views
Define a matrix in R in a similar fashon as with Numpy
I love the fact that using numpy in Python it is very easy to define a matrix/array in a way that is very close to the mathematical definition.
Does R have a similar way of achieving this result?
...
- 1,461
0
votes
1
answer
64
views
bottleneck in multiprocessing in python
I have a code that uses two parameters (r,t) to create a matrix H. I then find the eigenvalues of this matrix and do some computations using the eigenvalues. Now, I need to do this for many different ...
- 21
1
vote
1
answer
89
views
how to use efficiently rotation matrix in numpy to compute new coordinates along a circle (avoiding for loops)?
I would like improve the script below.
The goal of the script is to compute different coordinates corresponding to several angles. This corresponds to rotate one point around x axis and for each step ...
- 155
3
votes
3
answers
104
views
Finding unique columns and their indices in NumPy matrix efficiently
I have a very large binary matrix (for example, shape = (210000, 5000)) and want to find unique columns and indices of this matrix. Memory is important to me, so that is why I am looking for a method ...
- 31
0
votes
0
answers
46
views
Raising a Numpy Array to a large power [duplicate]
I am using Numpy to raise a 2 X 2 array (matrix), with positive elements, to an integer power. But if I use a high enough power, I get negative values in the result:
A = np.array([[1, 1], [1, 0]])
B = ...
0
votes
1
answer
35
views
How to reorder rows of a numpy array according to another array [duplicate]
I have a matrix A whose rows have to be reordered or shuffled according to the sequence in array b. The actual size of a Matrix A is more than 100 rows. The suggested answer need to be scalable.
A = ...
- 81
2
votes
2
answers
61
views
NumPy: get a matrix of distances between values
If I have a set of points:
points = np.random.randint(0, 11, size=10)
print(points)
Output:
[ 5 4 9 7 4 1 2 10 4 2]
And if I want to get a matrix representing the distance from each point to ...
- 844