# Bruno Luong

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**Content Feed**

For loop over permutations of 1:n with very large n

If you don't care about finding optimal solution, why not just do n = 1e15; % 1e18 has problem of coding as in my comment above...

ongeveer een maand ago | 0

find rows in a matrix where all the elements (of those rows) are not NaN

An alternative ways of testing a = [ NaN NaN NaN NaN NaN NaN NaN NaN NaN...

2 maanden ago | 0

Inverse wavelet transform using only one wavelet transform

I guess because you feed in random data, the scale cannot by estimate correctly therefore the first level of the scale (and also...

2 maanden ago | 0

try...catch for memory full error in imaq toolbox ?

To my knowledge there is no simple way to detect memory issue. What you ask MATLAB, e.g., using command such as [~,sys] = memo...

2 maanden ago | 0

What could be a faster way to calculate first derivative of a field?

dfdt = (f(3:end)-f(1:end-2))*(1/(2*dt))

2 maanden ago | 0

| accepted

Merging piecewise polynomial (pp) structures

Using BSFK from this FEX https://www.mathworks.com/matlabcentral/answers/1810010-free-knot-spline-approximation-bsfk-problem?s_t...

2 maanden ago | 1

How do you reshape an array to preserve the order in each row of the original array?

A = magic(3) reshape(A.', [],1)

2 maanden ago | 0

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3 subplots with the bottom one split in 2 vertically?

Plenty of examples are given in the doc page https://www.mathworks.com/help/matlab/ref/tiledlayout.html

2 maanden ago | 1

Speeding up matrix operations

Instead of calling trapz, use matrix multiplication, and this probably beats anything out there in term of speed and memory A =...

3 maanden ago | 1

| accepted

Speeding up matrix operations

All loops are removed, but the memory requirement might be an issue. As I don't know what mean "very large N, M" I can't make a...

3 maanden ago | 0

Construct a permutation matrix from two vectors

combinations, new stock function in R2023a a = [1 ; 2 ; 3]; b = [4 ; 5 ; 6]; combinations(a,b)

3 maanden ago | 1

How to extract diagonal elements of multidimensional array ?

N = 7; A = rand(N,N,N,N,N); p=ndims(A); N=length(A); % Method 1: generalization of cyclist's answer step = polyval(ones...

3 maanden ago | 0

How to avoid automatic conversion of complex to real?

Yes it works as intended, and no there is no way to disable it. This automatic conversion also affects the CPU and sometime it ...

3 maanden ago | 0

Is it possible to solve the problem on a permutation set with MATLAB tools?

@potato curious I have function like f(x) = 4x₁+3x₂ and constraints like 3x₁+5x₂<=20, x₁+6x₂>=30. And need to find which permuta...

3 maanden ago | 0

| accepted

Question

xregion yregion back/front control

I play with the new xregion command (R2023A) The red region is hide by the histogram, not sure why it is not as document exampl...

3 maanden ago | 1 answer | 0

### 1

answerHow to know interpolated points in a MATLAB plot?

% Dummy example of some curve that cross the horizontal line y=10 x = cumsum([0 rand(1,40)]); y = 12*sin(x); plot(x,y,'.-'); ...

3 maanden ago | 1

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minimum value optimization of matrix with constraints

Straighforward implementation, it seems more reliable than Matt's square-root parametrization. The square-root makes the gradie...

3 maanden ago | 0

| accepted

The most efficient way to calculate multiplication and summation of two large matrices

It is just a scaling of matrix multiplication, if you haven't recorgnize it A=rand(300,1000); B=rand(300,1000); tic C1=(A*...

3 maanden ago | 1

| accepted

Create random symmetric matrix with given cond number to pass it to pcg

n=10; % size of the system condtarget = 1000; % generate ransom spd matrix [Q,~]=qr(randn(n)); r = rand(n,1); r = (r-min(...

3 maanden ago | 0

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How to get a smooth plot by filtering the sudden variation of the data?

It recovers a big tail part of the signal. Hard to guess what should be the signal at the begining. A=readmatrix('https://www.m...

3 maanden ago | 0

FFT analysis with window of vibration during milling

I don't see the need of calling sgolayfilt. It is just a linear filter so it is equivalent to scale down the signal in frequency...

3 maanden ago | 0

natural cubic spline interpolation of y-values: how to get derivative of the spline wrt the y-values?

The derivative f wrt to y_i is the spline interpolate b_i := (0,0,...,1,0...) where 1 is at ith position, since the spline is li...

3 maanden ago | 0

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natural cubic spline interpolation of y-values: how to get derivative of the spline wrt the y-values?

In this thread https://fr.mathworks.com/matlabcentral/answers/1894800-how-to-remove-noise-from-curves-and-take-their-derivates?s...

3 maanden ago | 0

How to use isoutlier based in a part of the data?

Not sure, you are not better to describe what you want than most people; what you cann outlier seems to be point that violate th...

3 maanden ago | 0

Modified Akima Interpolation process

Just look at the refernce provided in the doc page A New Method of Interpolation and Smooth Curve Fitting Based on Local Proced...

3 maanden ago | 0

How to get around sparse row deletion for least squares calculation

I'm nit sure why you formalize as block sparse, since it is like solving d independent linear systems of the same size, and can ...

3 maanden ago | 0

Question

factorization of Multivariate polynomial

Hello, I want to factorize a multivariate polynomial in a complex field. I just don't understand why the result of this simple p...

3 maanden ago | 2 answers | 0

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answerswhat is a reasonable step tolerance for optimization algorithms if parameters are in the range [0,1]?

Your question is not clear enough. the official doc explains how it eaxctly works https://www.mathworks.com/help/optim/ug/toler...

3 maanden ago | 0

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Matrix multiplication gives different result than manual dot products with each column

"Does anyone know why these two expressions don't give the same answer? " Why should they? The algorithm can perform diffrent s...

3 maanden ago | 0

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Why do I see a drop in the last datapoint (Nyquist frequency) of the spectra derived from pwelch?

No I beg to differ the answers that have given to you. The reason is the convention of onesided spectrum. In the code computepsd...

3 maanden ago | 0