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John D'Errico


Retired

Last seen: Today Actif depuis 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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A répondu
how can i make ga to reproduce specific result?
No. You cannot enforce that GA will find any specific result. It appears you understand that GA may find different local solutio...

1 jour il y a | 0

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A répondu
Given a taylor series of a function f, how do I get the original function f
You CANNOT do so. I'm sorry, but you are asking the impossible. Looking at it another way, the solution is absolutely trivial. W...

1 jour il y a | 0

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A répondu
Gauss seidel method not working for sparse matrices
Um, don't use Gauss-Seidel? It is not that this matrix is sparse. (In fact, it was not even created as a sparse matrix. Sparsit...

2 jours il y a | 0

A répondu
Can using 'angle' to find S21 phase shift ever be done incorrectly?
Hint: Learn about ATAN2, why it exists, and what it does differently. Use of atan gives a 2 quadrant arc tangent. The point is,...

3 jours il y a | 0

A répondu
How to find a sequence from a txt file?
strfind does NOT read a string from a file! You did this: % Open the file fileID = fopen('cDNA1-1.txt', 'r'); % Rea...

3 jours il y a | 0

A répondu
Solving large number of equations
This is not even a remotely large number of equations. Will you please learn to use matrices? X8 appears in only one form in y...

4 jours il y a | 0

A répondu
Expected value with maximal domains
At the VERY least, you have chosen to MULTIPLY the two terms, instead of dividing them. Assuming you really wanted to form a rat...

5 jours il y a | 0

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A répondu
MATLAB does not run on new iMAC
You do not say what OS version you have on the iMac, though I can guess, since you say it is a new iMac. The problem is most li...

5 jours il y a | 0

A répondu
Will Quality of Documentation be better in 2024 Products?
If there is something specific that you think was lacking, then it is your responsibility to tell TMW what was missing. Don't ju...

5 jours il y a | 0

A répondu
How to get mesh used by integral function adaptive quadrature
Nothing stops you from recording the points sent into your integration kernel. Save them in a persistent variable, for example, ...

5 jours il y a | 0

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A répondu
Are the rules for element by element matrix operation changed?
Long ago, in a galaxy far, far away, we all used to use repmat to work with arrays of different sizes like that. Our code was go...

5 jours il y a | 1

A répondu
How can I ignore (delete) unwanted peaks of a continious signal?
Just choose some point where the curve should have settled into its long term nominal state. That should be at or about a time o...

5 jours il y a | 2

A répondu
I keep this fuzzy function error; "Undefined function or variable 'fuzzy'."
In keeping with a question about the fuzzy toolbox, my response is an oldie, but moldy. That is, do you actually have that toolb...

7 jours il y a | 0

A répondu
lines that meet each other
I think you have what is really a simple question. But you need to formulate it in mathematics, and that is often difficult with...

9 jours il y a | 0

A répondu
problem in curve fitting using summation of sine functions
I'll post this as a separate answer, so as to not get it lost in the comments, and since I will show you how to solve it as a tr...

9 jours il y a | 0

A répondu
problem in curve fitting using summation of sine functions
Ok. Thank you for the data. The plot does help a lot actually. At first glance, the plot of the fit itself looks quite reasonabl...

10 jours il y a | 0

A répondu
Why R square value is coming negative ?
Actually, not. R^2 can be negative for two potential reasons. If the R^2 was computed incorrectly. If the model is worse than...

10 jours il y a | 0

A répondu
ODE45 giving complex solution unexpectedly
This seems clear. The only way in your code you can generate complex numbers is by raising a negative number to a fractional pow...

13 jours il y a | 2

A répondu
optimization doesn't carry out using fgoalattain
Sigh. So many times this same question gets asked. :) Clearly not your fault of course, given the number of others who trip over...

13 jours il y a | 1

A répondu
What is the most cost effective way for an individual researcher to purchase fast compute for deep learning tasks?
No matter what, I would be looking towards a desktop machine. Then you get the advantage of adequate fans to keep those cores hu...

13 jours il y a | 0

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A répondu
some problem about the discrete of the first derivative operator
It is difficult to know, not without reading the article. Is the D matrix as shown just a typo that got by the proofreaders? Ve...

14 jours il y a | 1

| A accepté

A répondu
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...

14 jours il y a | 0

A répondu
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...

14 jours il y a | 0

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A répondu
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...

15 jours il y a | 1

A répondu
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 ...

15 jours il y a | 1

A répondu
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...

15 jours il y a | 0

A répondu
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...

15 jours il y a | 0

A répondu
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...

15 jours il y a | 0

A répondu
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...

15 jours il y a | 0

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