Questions tagged [numpy]
NumPy is the fundamental package for scientific computing with Python.
168
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How can I efficiently find an anti-symmetric generator of a special orthogonal matrix?
Given a special orthogonal matrix $O$ (i.e: $OO^T = 1$ and $\det(O) = 1$), I am trying to efficiently find a matrix $X$ such that $O = e^X$ and $X = -X^T$ using Python (NumPy & SciPy).
One obvious ...
- 227
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0
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Converting an expression into an einsum
I have the following expression that I need to calculate for some matrices:
$$
\sum_{k}c_{t,i,k}\sigma^\prime\left(w_tX_t+b_t\right)_k\left(\sum_\ell w_{t,k,\ell}\tilde{X}_t^{w,\ell}\right)
$$
I could,...
- 111
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First and second component of fft for circle approximation to periodic curve
I wanted to understand how the fast fourier transform work in numpy and for this I tried apply it on $n$ points of an ellipse $t_k = \frac{2\pi}{n-1}k$ with $k=1...n$ $$f_k = f(t_k) = (acos(t_k), bsin(...
- 173
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1
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Solving a polynomial with NumPy
I'm trying to do something that I thought would be very straightforward but somehow I'm struggling.
I have a time series and I want to extrapolate it, assuming a linear trend, to forecast when will it ...
user782
11
votes
1
answer
343
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Is it possible to express an arbitrary tensor contraction in terms of BLAS routines?
I noticed that libraries like numpy and pytorch are able to perform arbitrary tensor contractions at speeds similar to comparably sized matrix multiplications. This leads me to believe that underneath ...
- 121
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2
answers
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What algorithm(s) do numpy and scipy use to calculate matrix inverses?
I am solving differential equations that require inverting dense square matrices, and I wanted to know what algorithm(s) do numpy and scipy use to calculate matrix inverses?
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1
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Improvement to naive gradient descent implementation for the Thomson problem
I have a Python program (available on github) that uses naive gradient descent to find approximate solutions to the Thomson Problem. It works surprisingly well, but I've been wondering if there's a ...
- 229
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258
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Helmholtz decomposition of a vector field in Fourier space with Python
I have a 3D vector field and I want to extract its divergence-free part (also called transverse component), using the Helmholtz decomposition.
In principle, this can be done in the Fourier space, as ...
- 31
1
vote
1
answer
705
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Float equality tolerance for single and half precision
Suppose the metric is
abs(a-b) <= rtol * max(abs(a), abs(b))
i.e. math.isclose with ...
0
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1
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78
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Compute a series of matrix multiplications and matrix norms quickly in Python
I need to compute a series of matrix multiplications involving 3x3 matrices and a series of matrix norms also involving 3x3 matrices and I wonder how I can set these computations up with numpy such ...
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106
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Time and memory required to diagonalize a 18000 by 18000 matrix using numpy in python
Can someone give an estimate of the Time and memory required to diagonalize a 20000 by 20000 complex hermitian matrix using numpy in python ?
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Convolution/weighted average of two arrays in Python
I have an equation that I need to calculate numerically, but I am having doubts about my approach. I am cross-posting this question from Stack Exchange, because I am not getting any responses.
This is ...
- 105
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0
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Eigenvalues of same operator expressed in two different orthonormal basis are coming out different
I have an operator $H$. I express $H$ as a matrix in the orthonormalized $\{ |e > \}$ basis. Then I diagonalize it to obtain eigenvalues, let's say for example $H$ is $6 \times 6$ and the ...
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Beta function and integral value
I have two values $a$ and $b$ where $a \ge 0$ and $b \ge 0$ and I have to calculate the formula below.
$$
\frac{1}{2}\int_0^1\text{abs}\left[\left( \frac{p_i^{(a - 1)} \times (1 - p_i)^{(b - 1)}}{\...
