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John D'Errico


Retired

Last seen: Today Con actividad desde 2006

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 recover original raw signal from filtered results given filter coefficiencies?
Is it possible? NO. Sorry. Mathematics does not give you a trash can, where this operation can be undone. Information content wa...

alrededor de 7 horas hace | 0

Respondida
Inverse of a symmetric matrix consisting of submatrices is desired.
This makes little sense as you write it, AND it will be essentially impossible to perform in MATLAB using symbolic tools. syms C...

alrededor de 13 horas hace | 0

Respondida
Solving equations using Newton-Raphson method for 7 equations with 7 variables
As @Torsten said, this is a LINEAR system of equations. Nothing nonlinear needed. In fact, you can use many tools in MATLAB to t...

1 día hace | 1

Respondida
Need help with a system non-linear equation with three variables
Simple. Use lsqnonlin. There will almsot certainly be no exact solution. All you can do is find a parameter set that minimizes ...

1 día hace | 1

Respondida
read text file to get complex number
Read the files in as two vectors. There are many tools that can read a text file. Then add them, multiplying the second by sqrt...

1 día hace | 0

Respondida
GA does not solve problems with integer and equality constraints
The coupling of equality constraints with integer constraints makes a significant problem. For example, suppose I wanted to solv...

1 día hace | 0

Respondida
problem with low infinite number
They only look the same, to 4 decimal places. format short x = 1.23456789; y = 1.23456987; [x,y] They certainly look the s...

1 día hace | 0

Respondida
How to display this whole data simultaneously?
What can you do? This will mainly be in your MATLAB settings, first, under the command window tab. Here, you can control how man...

1 día hace | 0

Respondida
Fittype issue: unrealistic results and problems with upper and lower bounds
Star pointed much out to you, but I want to say a few extra things, and the fit he got was relative crap due to the terrible cho...

2 días hace | 1

Respondida
integration in matlab plot
You CANNOT use trapz. Despite the fact that another poster has done so, that does not yield a result up to 4.7. If you have no d...

3 días hace | 3

Respondida
2023b Compatibility with 2019b code?
Is there a limit? No limit is ever published. The first is a warning, NOT an error message. It is intended to tell you there wil...

3 días hace | 1

Respondida
Find Area under the curve as a non negative
You don't show your data, so I need to make something up, and I'm guessing what your problem is, because your question is confus...

4 días hace | 0

Respondida
Problem with non-Zero Matrix Appearing Zero in Command Window and in Imagesc
They are still (non-zero) numbers. Just too small to display in the chosen format. If you close your eyes, the world does not di...

5 días hace | 0

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Respondida
str2double with long string seems to give wrong answer
Do you appreciate that str2double will convert the number to a DOUBLE PRECISION number? Of course it must, as why would it conve...

5 días hace | 3

Respondida
How to use for and if statements together?
Can you compute the overall mean? Surely you know how to use the function mean. If not, can you compute the overall mean? How wo...

5 días hace | 0

Respondida
Why Matlab is always giving the same error while putting comment to reply in quesiton?
MATLAB is not doing anything of the sort. In fact, that is not a response from MATLAB at all, but from the web site, from MATLAB...

5 días hace | 0

Respondida
Solve a system of linear equations
I am confused. You say that you know how to solve the problem using lsqnonneg. So just use it! n = 30; Y = rand(30,n); S = r...

6 días hace | 0

Respondida
generating every possible trajectory in a workspace
Um, no. There are infinitely many possible trajectories, if we consider the variables as continuous. But even if all variables w...

7 días hace | 0

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Respondida
How do I request participation or sponsorship from MathWorks on behalf of my social organization at my University?
Answers is not the correct place to ask your question. Instead, I would contact support directly. Possibly through this link: h...

7 días hace | 0

Respondida
Solving tridiagonal Matlab matrix using Gauss siedel ( can't use other method )
Why in the name of god and little green apples are you using Gauss-Seidel for this? (I can only assume this is a homework assign...

7 días hace | 1

| aceptada

Respondida
How do I change my code so that the numbers 1112, 2111, 1211 or 1121 work in this code to reach Kaprekar's Constant?
Numbers in MATLAB do not have leading zeros. Sorry. That is not a valid number, just a string of numeric digits. If you need le...

7 días hace | 1

| aceptada

Respondida
What Does the Symbolic Math Toolbox Mean by 0 < s When s is Complex?
Just test it yourself. :) Admittedly, it may not have been obvious to perform this test. But we can use it to learn how MATLAB s...

9 días hace | 0

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Respondida
how can I calculate my expression with double integration?
The important takeaway to use is, you CANNOT perform arithmetic operations between a pair of function handles. Maybe you think y...

9 días hace | 0

Respondida
fsolve with bound constraints - transformation method
The transformation need not be one to one. For example, a common and reasonably good way to perform an optimization subject to b...

10 días hace | 0

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Respondida
How to get a random possible solution from 'solve' function when getting unknown parameters z1 and conditions
Solve cannot return a random possible solution. Wanting code to do what it is not designed to do will never be sufficient. If ...

10 días hace | 1

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Respondida
How to get a surface plot for the given function to know how many minima are there?
You cannot plot 4 independent variables. In fact, you would need 5 dimensions to plot, since you want to plot the result of that...

10 días hace | 0

Respondida
I can't comput the following commands
Sure you "can". It is just that MATLAB fails due to an error. :) Anyway, you seem to think an if statement applies to each elem...

10 días hace | 0

Respondida
How to plot four variable vector-valued function in MATLAB?
It is no problem. Well, at least not if you have a hyper-dimensional holographic monitor. (Mine is broken, and awaiting parts de...

12 días hace | 0

Respondida
Not auto change sec(x) to 1/cos(x)?
The problem is, which form is simpler? Simple in your eyes need not always be simple in the "eyes" of your computer. The point ...

12 días hace | 0

Respondida
How to count how often a variable returns to zero and then increases from zero
It appears this parameter never goes negative. Are your sets ALWAYS such that a zero is always alone? So when it hits zero, it ...

13 días hace | 0

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