Numpy universal functions are "vectorized" functions operating on elements (element by element) on a Numpy array.
Questions tagged [numpy-ufunc]
198 questions
2
votes
2 answers
How to apply a Pearson Correlation Analysis over all pairs of pixels of a DataArray as a Correlation Matrix?
I am facing serious difficulties in generating a correlation matrix (pixel by pixel) of a single Netcdf with dimensions ('lon', 'lat', 'time'). My final intent is to generate what one calls a Teleconnectivity Map.
This Map is composed of correlation…
Philipe Riskalla Leal
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2
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1 answer
Why is NumPy subtraction slower on one large matrix $M$ than when dividing $M$ into smaller matrices and then subtracting?
I'm working on some code where I have several matrices and want to subtract a vector $v$ from each row of each matrix (and then do some other stuff with the result). As I'm using NumPy and want to 'vectorise' as much as possible, I thought I'd speed…
grapher
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ufunc Vs basic arithmetic operators in Numpy
I see that Universal Function(ufunc) is used for performing element wise array operations.
arr = np.arange(5)
arr2 = np.arange(5,10)
np.add(arr,arr2)
This piece of code is similar to arr + arr2. In that case why should we use ufunc?
Meghana Bandaru
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Combining outer subtraction with element wise subtraction on the last axis?
import numpy as np
import itertools as it
SPIN_POS = np.array([[0, 0, 0], [1, 1, 0], [1, 0, 1], [0, 1, 1],
[2, 2, 0], [3, 3, 0], [3, 2, 1], [2, 3, 1],
[2, 0, 2], [3, 1, 2], [3, 0, 3], [2, 1, 3],
…
Troy
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2
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1 answer
universal function concept and notation in numpy
I'm learning numpy package, and I've found this code example:
import numpy as np
a = np.array([[1,2,3], [4,5,6]])
np.add.reduce(a)
The thing I'm unable to understand is the dot notation:
np.add.reduce(a)
in contrast with, for…
31173
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Disparity between result of numpy gradient applied directly and applied using xarray.apply_ufunc
I'm trying to use xarray's apply_ufunc to wrap numpy's gradient function, in order to take gradients along one dimension. However, apply_ufunc is returning an array with a different shape to the one which using np.gradient directly returns:
import…
ThomasNicholas
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Testing Numpy operations
Whenever I need to test a moderately complex numpy expression, say,
c = np.multiply.outer(a, b)
d = np.einsum('kjij->ijk', c)
I end up doings hacks such as, e.g., setting a and bthus
a = np.arange(9).reshape(3,3)
b = a / 10
so that I can then…
Schiphol
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2 answers
Fastest way to compare every element with every other in np array of strings
I have a numpy array of strings, some duplicated, and I'd like to compare every element with every other element to produce a new vector of 1's and 0's indicating whether each pair (i,j) is the same or different.
e.g. ["a","b","a","c"] -> 12-element…
Jess
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1 answer
Modifying pandas dataframe in place using numpy ufuncs
I have four columns with values: 'A', 'B', 'C' and 'D' and one column containing either of the four letters.
Letter A B C D max
12063289 D 5 9 0 39 0
12063290 D 3 25 0 79 …
tobsecret
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votes
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How do I ufuncify a function that contains LaTeX symbols?
This code
from sympy import symbols
from sympy.utilities.autowrap import ufuncify
a = symbols(r'\alpha')
phi = a**2
phi_f = ufuncify(a, phi)
throws the errors below, which are clearly coming from the \alpha in the Python/C code. Unfortunately, it's…
Michael A
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With Numba's `guvectorize` targeted to CUDA, how do I specify a variable as both input and output?
I want to use Numba's guvectorize method to run code on my CUDA card. I first defined a CPU method
from numba import guvectorize
import numpy as np
@guvectorize(['float32[:,:], float32[:,:]',
'float64[:,:], float64[:,:]'],
…
Steven C. Howell
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2
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Why is ones_like listed as a ufunc?
I was surprised to see numpy.ones_like listed in the list of ufuncs here. Is this just an oversight, or is there specific use case?
Benjamin
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Sympy - ufuncify a vector function
I have lambdify-ied a vector function of a modified FitzHugh–Nagumo model (with no diffusion terms):
from sympy import symbols, Matrix, solve, Eq
from sympy import diff, simplify, lambdify
from sympy.utilities.autowrap import ufuncify
u, v , e,…
Ohm
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Use numpy.frompyfunc to add broadcasting to a python function with argument
From an array like db (which will be approximately (1e6, 300)) and a mask = [1, 0, 1] vector, I define the target as a 1 in the first column.
I want to create an out vector that consists of ones where the corresponding row in db matches the mask and…
user3313834
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2
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What's the ufunc to do floor division in numpy with python3.x?
In python 2.x, I can use the universal function numpy.divide to do floor division. However, the ufunc divide and true_divide both do true division in python 3.x.
In [24]: np.divide([1, 2, 3, 4], 2)
Out[24]: array([ 0.5, 1. , 1.5, 2. ])
In [25]:…
Eastsun
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