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John D'Errico


Retired

Last seen: Today 2006 年からアクティブ

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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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回答済み
comparison between two optimisation algorithms
There are very, very many ways to solve a computing problem. You have chosen one of them, and it worked for you. Is the choice...

4日 前 | 0

回答済み
Strange behaviour of plot
Cute. If you try this in R2025a: small = 1e-7;plot([0,small,1],[0,small,1]) small = 1e-8;plot([0,small,1],[0,small,1]) (Sorry...

5日 前 | 0

回答済み
How does Matlabs svd() function calculate the value of V?
UM, You seriously do not want to use X'*X to compute anything about the SVD. Yes, mathematically, it is the same. But this is no...

6日 前 | 1

回答済み
icc rgb profile editing
You can use iccread and iccwrite. help iccread help iccwrite Having used iccread, you can modify whatever you wish, then writ...

6日 前 | 0

回答済み
How to reduce the file size of MAT files?
NO. Rounding numbers will change nothing. MATLAB does not store double precision numbers in decimal form. So even though you thi...

12日 前 | 0

| 採用済み

回答済み
select line by touching with mouse
"select curve?" Well, yes, in a sense. When you plot the curve, you can supply a ButtonDownFcn, so that when you click on the c...

12日 前 | 0

回答済み
Fitting a blackbody curve with two variables - having issues with lsqcurvefit stopping and unsure how to use options effectively
Your data does not seem to fit terribly well to the model you propose. c=2.998e8; h=6.6261e-34; kb=1.38e-23; %wavelgnth (x...

13日 前 | 1

| 採用済み

回答済み
How to generate all 2^n combinations of n choices from a 2-vector?
Simple enough. Don't use combinations. n = 3; t = dec2bin(0:2^n - 1) - '0' Easy enough to make that into a table if you so de...

16日 前 | 1

| 採用済み

回答済み
Matlab 'try now' and contact customer service doesn't work
Answers is not customer support. In fact, we are generally not even employed at The MathWorks, though some TMW staff do visit th...

18日 前 | 0

| 採用済み

回答済み
is readmatrix a built-in Matlab function part over every install after 2019a?
NO. Not for ANY release number. Some of those functions may have been introduced in different years, different releases. And if ...

19日 前 | 0

回答済み
Constraints to a Second Order Curve Fit
You want to constrain the quadratic coefficient to be positive. But your data wants it to be a little bit negative. Effectively,...

約1ヶ月 前 | 1

回答済み
Is vectorization worth the trouble with recent MATLAB?
Is vectorization worth it? Let me see. For example: Add 1 to every element of a vector. V = rand(1,1e6); % Which is itself high...

約1ヶ月 前 | 0

回答済み
How to specify intervals of increasing, decreasing of a function in MATLAB
This can get fairly messy, if your function is carefully designed to cause you problems. For example, you may need to find a sin...

約1ヶ月 前 | 1

回答済み
Not exactly the exact answer using Symbolic Math Toolbox
Your problem stems from a common mistake. Whaen you write this: syms t f = sin(t); frms = sqrt(1/(2*pi)*int(f^2,t,[0 2*pi]))...

約1ヶ月 前 | 1

回答済み
How does the expfit function... functions
You may be confused. Well, let me say, almost certainly, you are confused. ;-) There is a difference between curve fitting, in ...

約1ヶ月 前 | 0

回答済み
No results are showing in the symbolic math computation
First, you need to recognize MATLAB is case sensitive. Your code does not run, instead, it fails in several places. I fixed it, ...

約1ヶ月 前 | 0

| 採用済み

回答済み
Solving ODE just for one time step
Then I fail to see the problem. You want only the solution at the end point. % A simple ODE. with y(0) == 1, the analytical s...

約1ヶ月 前 | 0

回答済み
Analyzing errors of a numerical Jacobian matrix of partial derivatives, as the finite-differencing step-size gets successively smaller,
I explained EXACTLY this in my last answer to your last question. Please read what I write and think about it. If you don't then...

約1ヶ月 前 | 0

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How can I reduce the "method error" with my central-difference method, when estimating a Jacobian matrix of partial derivatives?
This is a complex question, with possibly no perfect answer. For example, suppose you have a Newton method, that employs a fini...

約1ヶ月 前 | 3

回答済み
Better package manager abstracted away from matlab versions
Why don't they have the perfect set of tools, exactly as you want them to have been written? Because MATLAB was designed to make...

約1ヶ月 前 | 0

回答済み
Generate n random numbers between 0.1 and 0.9 without repetition
There are always many ways to solve a problem. Here is mine: % generate the set of ALL possible combinations. There are not man...

約1ヶ月 前 | 0

回答済み
How to get real root of a function using fminbnd?
It sounds like you want to see the result: (-1)^(4/3) == 1 To do that, you want to use nthroot, by splitting the fraction...

約2ヶ月 前 | 0

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solving numerically non-linear equation , code below does not work
What does not work? This is just a basic Newton-Raphson method. First, what are the functions for your test problem? x^2 + y...

約2ヶ月 前 | 1

回答済み
Find the range of duplicates in a sorted element
I'll create a longer vector, with a few duplicates. V0 = randi(8,[1,15]) V = sort(V0) Now you want to know where the dups liv...

約2ヶ月 前 | 0

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What do you think of my numerical Jacobian, using the central-difference method?
What do we think of it? I'm sorry, but blech! Why? Don't number all of your variables! Don't create long lists of numbered var...

約2ヶ月 前 | 1

回答済み
Inverting an 8x8 symbolic matrix
What nobody ever seems to understand is that a symbolic inverse of a matrix like this grows exponentially in complexity. Many th...

約2ヶ月 前 | 3

回答済み
Is there any precomputation step on A'*(.)*A if matrix A is known, to speed up matrix computation A'*B_i*A in matlab with B_i denpends on the previous matrix B_{i-1}.
A is known and fixed, and apparently large, else you would not care about speed. The amount of memory on your laptop is irrelev...

約2ヶ月 前 | 0

回答済み
How to identify algorithm time complexity?
It is not at all trivial to determine the time complexity for SOME algorithms, at least not from merely knowing the method emplo...

約2ヶ月 前 | 0

回答済み
Where to Find a Dataset of High-Quality MATLAB Code for Training an LLM?
Looking at your question a second time, it is about MATLAB in a sense. in that you are looking for a repository of code to train...

約2ヶ月 前 | 0

回答済み
Logic Code required to be run in finite time
I think you misunderstand an important idea of computing. You NEVER want to use brute force on big problems. Those problems alwa...

約2ヶ月 前 | 1

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