John D'Errico

Retired

Last seen: Today | Active since 2006

Followers: 36 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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Answered
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...

2 days ago | 1

Answered
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 ...

6 days ago | 1

Answered
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...

9 days ago | 1

Answered
Obtaining the differential equations from graphical representation of the problem
Can you show that a set of equations is a valid representation of some data, merely by comparing them to a curve you find in som...

9 days ago | 0

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Answered
Will the old-style class definitions be supported in future version of Matlab?
One thing you cannot realistically ask on Answers (if you expect a fully valid answer) is what decisions about MATLAB will be ma...

12 days ago | 1

Answered
Modelling a system of differential equations with recurrences in matlab
This is known as a delay differential equation. You will find any solvers for them starting with the letters dde. help dde23 Y...

14 days ago | 0

Answered
Iterating the eigenvalue function (eig) produces patterns --- is this a well known result?
I'd have a hard time believing this is well known. @Christine Tobler would be the one to know though, and she agrees. It just f...

18 days ago | 0

Answered
Question on the format of 2D curve fit equations in plot
Scientific notation. 6.588e + 06x^2 == 6.588*10^6 * x^2 Note that it is easier and faster to write, and even a bit easier to ...

25 days ago | 0

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Answered
How do I find the average of a vector of units by using a for loop?
When you create a variable name, NEVER, NEVER, NEVER use a name that is an existing and useful function name. (Well, it might be...

27 days ago | 0

Answered
how to find orthonormal vector with condition?
Confusing question. Which probably means I'm misunderstanding your goal here, or that I am myself confused, which is not uncommo...

1 month ago | 0

Answered
Closed contour with least square differences to dataset
This can be quite difficult if you have some completely arbitrary form. But you tell us this is a simple closed form. And as lon...

1 month ago | 0

Answered
MATLAB R2018a needed
We cannot give you a copy of MATLAB. Answers is not customer support anyway. And even they don't just give out copies for anyone...

1 month ago | 0

Answered
[coeffA,scoreA,latentA] = pca(X);
The editor likes to complain. Just the kind of program it is. Think about this as a suggestion, a hint, in case maybe your code...

1 month ago | 0

Answered
How to define 1-bit variable in data dictionary?
MATLAB does not have a true 1-bit data class. Even a logical, which is clearly a 1 bit thing, thus either true or false, is sto...

1 month ago | 0

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Answered
Polyfit isn't adjusting to decreasing sinoidal data
Do you appreciate just how NON-polynomial-like this data is? Your data appears to be a variation of decaying sinusoid. While, ...

1 month ago | 0

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Answered
Precision Loss in Arithmetic Encoding of Binary Vectors for Reversible Data Hiding in 3D Meshes
You are telling us that you effectively have a binary number with 7000 binary bits. You convert it to a decimal number, and then...

2 months ago | 0

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Answered
SVD to a matrix subset (rows)
No, I don't think you can easily find the SVD of a subset of the rows of a matrix, based on the SVD of the full matrix. At least...

2 months ago | 2

Answered
I can not say wether Eigs is giving expected results or not
It is literally trivial to get large differences there. We need not even use eigs. Eig will suffice. A0 = randn(6); A0 = A0 + A...

2 months ago | 2

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Answered
How to correctly find the solution of a system of equations containing trigonometric functions
It was smart of you to look at the results, and question them. Always think about what comes out from a solver. Does the solutio...

2 months ago | 0

Answered
Analytic solution of quatric polynomial does not add up
One of the things you need to learn about symbolic algebra, is two expressions may not look the same, but that does not mean the...

2 months ago | 0

Answered
Function requires a Toolbox for which you do not have a license
If you could use it in the past, then you had a license for that toolbox. You cannot use a function from a toolbox where you lac...

2 months ago | 0

Answered
save a cmyk image in jpeg
No. Imwrite cannot save a CMYK image to JPG. However, it can save a 4 channel image to a PNG format. Then I would open the image...

2 months ago | 0

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Answered
Help with Difference Equation in MATLAB
Since V_i and h_i appear to vary with the index i, there is no analytical solution. (If V and h were constants, not changing wit...

2 months ago | 0

Answered
Unexpected results using SVD to separate components that make up a function
Yes. You do misunderstand how svd works, and what it produces. As well, I think you misunderstand what a rank 1 matrix means. A...

2 months ago | 1

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Answered
Why does DC offset occur when integrating AC signals in MATLAB/Simulink?
It looks like you want to integrate what appears to be a sine wave. You did that, expecting to get a pure cosine wave, Right? ...

2 months ago | 2

Answered
fill function sometimes working and sometimes not working, why?
Seems trivial to me. (Ok, easy. Triviality is in the eye of the beholder.) I don't give a hoot about how many real roots it has,...

3 months ago | 0

Answered
how to manage fzero output
I'd argue you are thinking about this the wrong way.You see that fzero has a problem, so you think you need to do something to f...

3 months ago | 0

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Answered
Inquiry on Time Complexity of cumsum
There is no (good) answer to your question. And that answer will subtly change next year too, with the next release of MATLAB, o...

3 months ago | 2

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Answered
Effect of rng on Genetic Algorithm
Let me expad on what @Walter Roberson said. There is no optimum seed, that is one seed that will be perfect for any problem. In ...

3 months ago | 0

Answered
where is the setting to page/summarize large tables?
We don't want you to go nuts. But, I'm a little surprised, as tables do what you want already by default, using R2025a, on my co...

3 months ago | 0