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John D'Errico


Last seen: Today Actif depuis 2006

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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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Réponse apportée
Error while outputting graph
Not very clear exactly what you are trying to do. I'm pretty sure you want to substitute in different values of the undetermined...

environ une heure il y a | 0

| A accepté

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Does anyone know why no matter what I change, I cant get dsolve to work?
I dropped out some of the stuff you did that was unnecessary. For example, the first line creates y(t), and implicitly also defi...

environ 3 heures il y a | 0

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What is the ECCN of Matlab 2014
I would argue that any release of MATLAB will live under the same ECCN. The wording in no way applies only to the current releas...

8 jours il y a | 0

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Lake America used as a name in Mapping Toolbox
I know enough people at MathWorks to believe they will not be bullied into such a stupid thing. Ok, I hope not, trusting in the ...

11 jours il y a | 1

| A accepté

Réponse apportée
Nonlinear Newton solver fails near resonance for porous moonpool model
Um, so what should we do? First, Newton's method is generally a great scheme. (You even understand that aspect from what I read ...

11 jours il y a | 0

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How to multiple very large numbers in Matlab?
Remember that Excel, just like MATLAB, is representing those numbers in a double precision form, and that limits you to roughly ...

14 jours il y a | 0

Réponse apportée
Histogram gives a wrong result?
Never assume that two mathematically identical floating point numbers will, if computed using different expressions, produce the...

24 jours il y a | 0

| A accepté

Réponse apportée
Please help me determine positive values of s and h(s,h>0) such that L1 and L2 have opposite signs. Then print L1 and L2
What have you tried? Look carefully at what you have. Take it apart, one piece at a time. a1=0.2494; a2=0.75; a3=0.01; a12=1.69...

environ 2 mois il y a | 0

Réponse apportée
What exactly does ε represent in numerical computing
Just to add some more info... For example, pi(x) is known as the prime counting function to some, the number of primes less tha...

environ 2 mois il y a | 0

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Why does parfor slow down with large shared arrays?
I can't test this myself, and I lack a great understanding of the parallel tools. But it looks like there are a few issues, main...

environ 2 mois il y a | 0

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How to get abbreviations into vars?
Can you just exclude a term just by looking at it, without knowing the parameters in it? Given the complexity of the mess you ha...

environ 2 mois il y a | 0

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Why is vecnorm So Slow?
The jump is often a question of algorithm changes. You would be surprised how often algorithms exhibit nonlinear breaks. As I re...

2 mois il y a | 1

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HDL coder support for Microchip high level synthesis tool SmartHLS
I'm sorry, but Answers is not a team. And we have no access to any information about timelines or any knowledge of when a given ...

2 mois il y a | 0

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why does factor(1) return 1? shouldn't it return null?
Yes, I agree, in that f1 = factor(1) could arguably return empty. 1 is not indeed prime, and so the result is inconsistent wit...

2 mois il y a | 0

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solve() returning empty, does a solution exist?
Just because solve returns empty does not mean a solution does not exist. In fact, most relations you can write down have absolu...

3 mois il y a | 1

| A accepté

Réponse apportée
Saving my path for future sessions.
The trick here is to use the help, because it teaches you what to use, at least it gives you a hint at how to solve it. If you m...

3 mois il y a | 0

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Help using the toeplitz function
20x20 is not large by any measure I would ever imagine. 20000x20000 might be large. :) Of course, large is a purely subjective a...

3 mois il y a | 0

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MATLAB Randomly Changes Values in Array to Scientific Notation
It is literally a certainty that some of those values are only approximately integer. No question in my mind. And is certainly n...

3 mois il y a | 0

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Réponse apportée
How to call kummerU for a stand alone program
You cannot do it from MATLAB, as stated by others. However, it looks like python does offer similar functionality. And I believe...

3 mois il y a | 0

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Can I solve a symetric system using only the lower triangular portion of the matrix?
You don't show your matrix. Only a picture of it, and a picture is not quite worth a thousand words all of the time. ;-) But co...

3 mois il y a | 0

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free trail doubt issue
After it ends in 30 days, it will just end. You will have a choice then of continuing your use of MATLAB by paying the normal fe...

3 mois il y a | 0

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Volume and Surface Area of a Compound Geometric Object
First, alpha shapes tend to be poor at representing volumes with sharp internal corners, like those between the intersection of ...

4 mois il y a | 1

Réponse apportée
Call parameters by their variable name in Simulink rather than having to index the value.
If you can pass in a vector, then you can pass in a structure. Just assign fields to the structure. parameters.khch = 2; There...

4 mois il y a | 0

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looking for creator of specific code
The codes I did find were a bit more sophisticated in general, and I did not expect to find anything. HOWEVER, when I looked on ...

4 mois il y a | 1

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¿Cómo podría solucionar matrices por el comando [L,U]? no sé nada respecto al tema
I think your confusion stems from a misunderstanding. LU is fine, even with rank deficient matrices. As long as you use the MATL...

4 mois il y a | 0

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Convergence error in numerical method.
99,9% probable user error, 0.1%, it could be real. Hey we cannot know, since we don't see your code. But the point is, you hav...

4 mois il y a | 1

Réponse apportée
Minimally constraining an FEA Model in Matlab
If it is resting on a surface, it is not resting gently, in the sense that it CANNOT freely expand below the surface. In fact, y...

4 mois il y a | 0

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Find specified number of points on curve with identical chord length (not arc length)
Admittedly, interparc does not solve the problem you want to solve. At least, not the probem you CLAIM you want to solve. As the...

5 mois il y a | 0

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can this code be improved?
You have asked several questions. 1. Is it well written? 2. Can it be improved? Something you did not ask is if it SHOULD be imp...

5 mois il y a | 0

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Eigendecomposition not fully utilizing all cores on M1 pro, matlab 2025b
Some operations are not as easily parallelized when utilizing automatic mutithreading. That is possibly the case for eig, where ...

5 mois il y a | 0

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