John D'Errico

Retired

Last seen: Today | Con actividad desde 2006

Followers: 28 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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Respondida
how to design digital filter
Are there free toolboxes to do filter design? You might find something on the file exchange, and what you find there comes at ...

4 días hace | 0

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why does this not work?
It failed because datetime did not recognize that string as a list of distinct times. Just because you know what you want code t...

5 días hace | 3

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Solving for a variable in an equation
First, you need to recognize there is NO analytical solution to your problem. So using solve means it will just toss and turn fo...

6 días hace | 0

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Does inverse modelling is possible with ANFIS?
In general, absolutely no. This is impossible. Why do I say that? Consider even an absolutely trivial linear model. I don't need...

9 días hace | 0

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Why is vpa not converting double accurately?
Quite interesting. When I first saw the title, I assumed it would be an obvious mistake. Then I saw the poster, and knew it woul...

10 días hace | 1

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finding partial solutions from ill-conditioned equations
The largest subset? It may be impossible to compute ANY subset accurately. You may be able to only compute a linear combination ...

13 días hace | 0

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What is evaluated to standard output is not being assigned to my variable
This is a not uncommon misunderstanding about cell arrays. d = {'.'; '..' '2022' '2024' '2025'} b = d(3:end) % the "righ...

19 días hace | 1

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Create similar curves through specific data points
The question is becoming more clear now, based on your response to my first answer. I'll post this as a separate answer, since t...

28 días hace | 0

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Respondida
Create similar curves through specific data points
You have asked a confusing question, which usually means you are yourself confused, perhaps about what you really want to do. It...

29 días hace | 0

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Solving linear system modulo prime^n when matrix is univertable
You can't use LU anyway, since it is not designed to work on that problem. Nor can you use slash or backslash, which again, do n...

alrededor de 1 mes hace | 0

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Differentiating inside a matlab function
Oh, you were so close. Actually, you did not even need to tell diff what variable to differentiate with respect to. syms x(t) ...

alrededor de 1 mes hace | 0

Respondida
How to generate an prime random number??
A random prime? Impossible to do. That is, something that many seem to misunderstand is you cannot generate a random number on s...

alrededor de 1 mes hace | 0

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How to make multiple lines of best fit into one scatter graph
Is it possible to do in MATLAB? Of course it is. It of course depends on the skill of the person writing the code. It depends on...

alrededor de 1 mes hace | 0

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Find best fit curve from multiple curves of different size
On the right end, you have an infinite slope. On the left end, not so much of a problem. But it will be better to do a couple of...

alrededor de 1 mes hace | 0

Respondida
How does interp1 work?
Why not post the actual data you used that caused the problem, instead of only a tiny fragment of it? You certainly CAN post t...

alrededor de 1 mes hace | 2

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Matlab Dimpulse function documentaion not found
It seems dimpulse (or at least one version thereof) can be found in the control TB. which dimpulse -all However, given the loc...

alrededor de 1 mes hace | 0

Respondida
part 3 example was wrong
Answers is not official MATLAB support. So telling us a problem exists does nothing. Contact support directly. https://www.ma...

alrededor de 1 mes hace | 1

Respondida
I'm trying to find solutions to variables in a system of non linear eqations, that represent a geometrical puzzle.
A problem is, we don't actually know what is the geometric system you are trying to solve, nor have you told us the solution you...

alrededor de 1 mes hace | 0

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Integrating a very long expression containing symbolic values
Is there some law of mathematics that everything you can or will write down has a solution? (No.) That int did not find a soluti...

alrededor de 1 mes hace | 0

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Can someone help me fix my bisection function?
Good code. Well, at least in terms of the documentation. Excellent in that respect. Readable code is important when you need to ...

alrededor de 1 mes hace | 0

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What is the interpolation algorithm behind MATLAB’s pcolor with FaceColor = 'interp' that creates sharp, defined boundaries？
There are three simple ways to interpolate inside a 2-d rectangular region. But two of them are analogues of each other. First,...

alrededor de 1 mes hace | 0

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How to compute the characteristic equation given the eigenvalues?
You have not asked this question as if it is a homework assignment, so I'll give an answer. The characteristic equation GIVEN e...

alrededor de 1 mes hace | 0

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How to download old version of toolbox?
You cannot. That is, you cannot use an old toolbox for a previous release in a newer release of MATLAB. So what can you do? You...

alrededor de 1 mes hace | 0

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Bug with large HEX numbers
H = 'fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141'; numel(H) So 64 hex digits, which would yield an intege...

alrededor de 1 mes hace | 1

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How to get consistant results when testing code performance
A single time test will be susceptible to anything that attracts the attention of your CPU. And sadly, your CPU suffers from com...

alrededor de 1 mes hace | 0

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update guess in fsolve
Um, no, You cannot always find a way to "update" your initial guess for fsolve. One can even prove this to be true. You can cha...

alrededor de 1 mes hace | 1

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How to remove columns in very large matrices.
GET MORE RAM!!!!!!!!! RAM IS CHEAP!!!!!!!! Need I say it again? You have a quite large array. (1.75e6*2000*8)/1e9 That arra...

alrededor de 2 meses hace | 1

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using sparse matrix and vpa function simultaneously
I wanted a nice bright red Lambo for Christmas. Nope. Did not happen, nor was it ever going to happen. The same applies to you. ...

alrededor de 2 meses hace | 0

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Respondida
Matrix is singular to working precision
I don't even need to run your code, to see an obvious mistake. In fact, I knew what I expect to be a problem, even before I look...

alrededor de 2 meses hace | 0

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real and integer variables
No. We won't do what is surely your homework assignment. But why not TRY IT! First, plotting it is trivial. LEARN TO USE a tool...

alrededor de 2 meses hace | 0

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