John D'Errico

Retired

Last seen: Today | Actif depuis 2006

Followers: 41 Following: 0

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A retired applied mathematician, consultant, sometime mechanical engineer, numerical analyst, woodworker, bridge player. Please DON'T contact me, as too many students then decide I am their personal consultant if I allow it. I won't do consulting by mail.

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GA stops with different score every time, even with setting big MaxGeneations and MaxStallGenerations
Nonlinear solvers, of which GA is one, cannot be forced to ALWAYS return the optimal result. And while tools like GA are designe...

1 jour il y a | 1

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Does [V,D] = eig(A) always return normalized eigenvectors for any real matrix A?
Be a little careful that A is not in symbolic form, even if it is real and SPD. A = randn(4,3); A = A'*A % A MUST clearly be SP...

1 jour il y a | 1

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Is fit() deterministic when StartPoint is specified?
If the start point is specified, then yes, FIT should be deterministic. At that point there is no reason for any pseudo-random n...

3 jours il y a | 2

Discussion

What is an emirp? Can we find a new world record size prime of this form, using only MATLAB, and a home computer?
An emirp is a prime that is prime when viewed in in both directions. They are not too difficult to find at a lower level. For ex...

5 jours il y a | 0

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fread a double that's been broken up into four 16 bit words
I don't see the problem. For example... Xtest = randn*100 Now, I'll split it into 4 hex numbers, each taking up 16 bits. Xhe...

9 jours il y a | 0

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vpasolve does not solve simple equation
Well, look more closely at your question. Plot it. syms x; A = 6.742; B = 4.82; F = A - 2/(9*(1 - x)^(1/2)) - B*x fplot(F,[0,...

20 jours il y a | 0

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Any way to remove terms smaller than "digits" from symbolic expression? R2023a
While the solutions offered by @Paul and @Walter Roberson will both solve the problem you asked, be careful, as automatic approa...

environ un mois il y a | 0

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When I use nlinfit, the sintax nlinfit(t0,p0 ,@(b,t) ...),but if Ireplace nlinfit with fmincon, the sintax is not valid, why?
@Marcos there is no need to use global variables. For example... x = rand(20,1); y = 3 + 4*exp(x*1.5) + randn(size(x))/3; plo...

environ un mois il y a | 0

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Como puedo reiniciar mis cursos
"I took a course last year, completed it, and received the corresponding certificate. However, I need an updated certificate for...

environ un mois il y a | 1

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Mixing name/value pair syntax
I have at least a couple of reasons why, which is why I will pose this as an answer. Knowing exactly which deliberations were ma...

environ 2 mois il y a | 0

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**How can inflection points be robustly identified on a cumulative histogram (CDF) curve in MATLAB when only discrete, noisy CDF data is available?**
I'm sorry, but you are looking for magic that does not exist. An inflection point is a point where the SECOND derivative chang...

environ 2 mois il y a | 1

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Convex bivariate B-spline by construction (PSD Hessian)?
Even without thinking about it, I'm pretty sure the answer is no. Things get nasty when you move beyond one dimension, and 2d is...

environ 2 mois il y a | 0

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An easy way to input song chords into a structure of MATLAB
AVOID the function input. It only hurts your code, preventing you from growing. Learn to use other solutions for data input. One...

2 mois il y a | 2

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I'm using a 2020 Mac Mini. Will R2017a run on this computer if I upgrade to MacOS Tahoe?
No. 2017a will NOT run on Tahoe. Just read the docs to tell you which OS versions can run R2017a. https://www.mathworks.com/co...

2 mois il y a | 0

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Are iterative methods always better than direct methods for solving large linear systems?
The use case which some may miss here, is the very large array, where a dense solver fails due to memory, but even the sparse on...

2 mois il y a | 2

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solving a system of linear equations where A is a 40*40 sparse matrix
I'd suggest that sparse is almost meaningless when the matrix is only 40x40. At that point, the dense solvers are still extremel...

2 mois il y a | 3

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Putting spaces between elements of a string/
A = ['011001110000';'101111000000';'110100011000';'011010001100';'010101000110';'110010100010';... '100001010011';'10100010...

2 mois il y a | 2

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How to download the certificate
I'm sorry, but no, we cannot resolve your problem. Answers is not customer support. Answers is a volunteer forum, generally comp...

3 mois il y a | 0

A soumis

HPF - a big decimal class
High precision floating point arithmetic, a new class written in MATLAB

3 mois il y a | 25 téléchargements |

4.9 / 5

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Defining inequality constraint A*x <= b for genetic algorithm
As I said in my comment, you cannot set up a linear system of inequalities to constrain that curved path from self intersections...

3 mois il y a | 0

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i want to add cplex and yalmip on my mac how ?
YALMIP is an external toolbox, written in MATLAB, so it could in theory be used by any MATLAB installation. However, it is proba...

3 mois il y a | 0

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flag a question as answered.
While DGM gave a very complete answer, worthy of acceptance in my eyes, I think, from a look at one of the other questions from ...

4 mois il y a | 1

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Finite elements model using STABIL
I cannot test your code, as I lack the tools you are using. Regardless, IF you tell us the solve yields NaNs, then there are onl...

4 mois il y a | 0

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Using logic to select specific values in a matrix
Well, you are doomed to failure, as long as you don't use the right variable names as you created them! A = [1, 0.1234 1,...

4 mois il y a | 0

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In how many functions using the global variable, can a global variable be declared?
There is no limit on how many functions can use a global variable. At the same time, I will plead, for your own sanity, to recon...

5 mois il y a | 1

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How do I plot a graph with the grid for trig functions with 0 ≤ x ≤ 2π
@Sean syms x f = cos(x) dfdx = diff(f) help fplot

5 mois il y a | 0

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Should I need keep in my PC previous versions of Matlab?
Some of us keep older releases, just to answer a question about an older release, testing out code in the old release. I do ten...

5 mois il y a | 0

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Unable to fetch more decimal points for values stored in sldd
You need to learn about the format command. All of the digits are still there, they were just not reported. I'll add a few digit...

5 mois il y a | 1

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The symbol "1" is not a scalar in integral3
If ALL you want to do is compute a volume, especially of such a simple domain, there are better ways to do so. If the domain is ...

5 mois il y a | 1

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How does the svd function determine or fix the phase of singular vectors?
First, signs are to some extent arbitrary. That is, for EIG, you can multiply an eigenvector by -1, and it is still an eigenvect...

5 mois il y a | 1

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