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Questions tagged [numerical-computing]

Is an interconnected combination of computer science and mathematics .

Is an interconnected combination of computer science and mathematics in which we develop and analyze algorithms for solving important problems in science, engineering, medicine, and business, for example, designing a bridge, choosing a stock portfolio, or detecting tumors in medical images

146 questions
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Optimize operations with arrays in numpy

I have to apply some mathematical formula that I've written in python as: for s in range(tdim): sum1 = 0.0 for i in range(dim): for j in range(dim): sum1+=0.5*np.cos(theta[s]*(i-j))* …
user2820579
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QuickHull worst case

QHull (and perhaps other good implementations of QuickHull) works really well and fast in many cases. However, we know theoretically that its worst case can be O(n^2). In practice I have not seen any numerical example with many dimensions (i.e., 20…
Alef
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Load sparse scipy matrix into existing numpy dense matrix

Say I have a huge numpy matrix A taking up tens of gigabytes. It takes a non-negligible amount of time to allocate this memory. Let's say I also have a collection of scipy sparse matrices with the same dimensions as the numpy matrix. Sometimes I…
conradlee
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How to tell how small `h` is the in the finite difference?

I'm doing a project required to compute the precise(up to a certain precession N) numerical derivatives of a function. The usual approach was to use the finite difference types of algorithms, i.e. (f(x+h)-f(x))/h However, there's not many document…
ShoutOutAndCalculate
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Should one calculate QR decomposition before Least Squares to speed up the process?

I am reading the book "Introduction to linear algebra" by Gilbert Strang. The section is called "Orthonormal Bases and Gram-Schmidt". The author several times emphasised the fact that with orthonormal basis it's very easy and fast to calculate Least…
mathgeek
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How to compute Brjuno function in Maxima CAS?

I try to compute real 1-Brjuno function for real numbers in x in [0, 1] range G(x):= block( [g], if (x=0) then g : 0 else g : float(1/x - floor(1/x)), return( g) )$ bet(j,x) :=…
Adam
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fortran : invalid memory reference

I encountered this error while solving the diffusion equation on fortran using alternating directional implicit(ADI) method. Program received signal SIGSEGV: Segmentation fault - invalid memory reference. Backtrace for this error: #0 …
이종훈
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Filling pixels under or above some function

Seems like a simple problem, but I just cant wrap my head around it. I have a config file in which I declare a few functions. It looks like this: "bandDefinitions" : [ { "0": ["x^2 + 2*x + 5 - y", "ABOVE"] }, { "0":…
Riki
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Accurate sqrt(1 + (x/2)^2) + x/2

I need to compute sqrt(1 + (x/2)^2) + x/2 numerically, for positive x. Using this expression directly fails for very large values of x. How can I rewrite it to obtain a more accurate evaluation?
a06e
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How to ensure my optimization algorithm has found the solution?

I am performing a numerical optimization where I try to find the parameters of a statistical model that best match certain moments of the data. I have 6 parameters in total I need to find. I have written a matlab function which takes the parameters…
fes
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Numerical Integration - Summations and Functions in Python

Forgive my ignorance, but the function H is actually an infinite sum (including -n terms). I'm hoping to truncate at larger values on the order of the 100s ideally. My code seems to work but I am not sure if it is actually summing over the values of…
AlphaArgonian
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Is Romberg integration method implemented as weighted function values numerically correct?

I have to integrate expression f(x) * g(x) for many different functions f but just one g. I want to integrate it as sum of weighted values of f(x) * g(x) instead of calculating the table. Note that in Python I may write: sum(w[i] * f(x[i]) *…
abukaj
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Function fzero in Matlab is not converging

I am solving a problem in my Macroeconomics class. Consider the following equation: Here, k is fixed and c(k) was defined through the ```interp1''' function in Matlab. Here is my code: beta = 0.98; delta = 0.13; A = 2; alpha = 1/3; n_grid = 1000; …
Raul Guarini Riva
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How to solve large nonlinear equations?

I have 3 large nonlinear equations with three unknowns, when I scipy.optimize.fsolve I obtain an answer around 10^85 which is too large. A Runtime warning is thrown as well. import scipy.optimize as opt def func(variables): (A, B, C) =…
mahdi bagheri
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Divide and Conquer SVD in MATLAB

I'm trying to implement Divide and Conquer SVD of an upper bidiagonal matrix B, but my code is not working. The error is: "Unable to perform assignment because the size of the left side is 3-by-3 and the size of the right side is 2-by-2.…
dxdydz
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