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John D'Errico


Retired

Last seen: Today 自 2006 起处于活动状态

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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已回答
Precision Difference Between MATLAB and Simulink MATLAB Function
No. This is not a difference in the precision used. Both tools will use double preicsion arithmetic to store all numbers. Inste...

4 hours 前 | 0

已回答
gamma function with two parameters
There is no common definition of a two parameter gamma "function" in mathematics. So whatever you are asking, you need to be mor...

9 hours 前 | 0

已回答
How to get x value for a given y value in a interp1 figure?
You need to understand there is no unique solution. So asking for THE value of x has no answer, since there are two possible sol...

10 hours 前 | 0

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已回答
3D plot with the Earth in the center
With the mapping toolbox, easy. Without the mapping toolbox, more difficult. Nothing is impossible, of course. But lacking the ...

1 day 前 | 0

已回答
How to draw a map of a country and mark the location of an object on it?
Do you have the mapping toolbox? https://www.mathworks.com/products/mapping.html Your question is easy to answer with that too...

1 day 前 | 0

已回答
I want to download Matlab 2019or 2021 or 2020 for my macOs monterey 12.6
There is a button that allows you to download previous releases. On the upper right of the page as I recall. HOWEVER, it also l...

1 day 前 | 0

已回答
How can I subtract elements in an array from the element before it.
help diff

2 days 前 | 1

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已回答
How to write in Matlab a matrix whose coefficients depend on a real alpha parameter
Many ways. It seems unclear exactly what is your goal. And what are x and y? Are they just a list of numbers? Or a sequence as l...

2 days 前 | 0

已回答
how to build a magic matrix manually of even n*n matrix?
@the cyclist is correct, that this is purely an algorithm question. But you did write code. Anyway, I'd start here, if I were y...

3 days 前 | 0

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已回答
How do I plot the cross sectional area and centroid of an I-Beam using pgon ?
The funny thing is, your code was indeed essentially correct. You just started out wrongly. x = [ 0 0 1 1 2 2 3 3 4 4...

3 days 前 | 0

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已回答
I got Inf when calculating 13959^475, how can I solve this problem?
Yes, you can use syms. However, you do NOT want to compute a huge power using syms directly, and THEN compute a modulus. Just co...

4 days 前 | 0

已回答
Error With Least Squares Approximation
There are two serious issues in what you are doing, making this apprach, sadly, truly numerical nonsense. You think you did some...

5 days 前 | 0

已回答
I unable to get trial version. Can you help?
No. We cannot help you. We are not your local customer support representatives! Answers is just a volunteer forum. We have no ...

5 days 前 | 0

已回答
Initial Conditions for Newton Raphson Method for 9 equations 9 unknowns problem set
Not every system of equations you will write down has a solution. Starting from a random position does not insure you will find...

6 days 前 | 0

已回答
Average Optimization using GA or intlinprog algorithms
This is not an optimization problem. You only look at it in that way. It is purely a problem of a Monte Carlo simulation, to com...

8 days 前 | 0

已回答
MacOS(14.0) and Matlab 2014a format problem
R2014a does not run on that recent of the Mac OS. It is not supported there, and in fact, I am surprised it even comes that clos...

8 days 前 | 0

已回答
Can multiple versions of MATLAB be installed on the same Windows PC using the same license number for code compatibility?"
Yes. I frequently have multiple releases on my machine. It is occasionally useful, but the older releases are usually there in m...

9 days 前 | 0

已回答
how to use lsqcurvefit on a function that contain a series
You only have ONE data point. xdata=420; ydata=0.1; So only ONE piece of information! How do you intend to estimate TWO param...

9 days 前 | 0

已回答
how does this work some clarification
Honestly, this Cody answer is one of the reasons why I think Cody is seriously flawed. It encourages people to write obscene cod...

9 days 前 | 1

已回答
Alternatives to syms?
Well, it is pretty old, but you COULD just use my sympoly toolbox. ;-) It is on the FEX for free download. (Pretty old by now, b...

9 days 前 | 2

已回答
Critical points of level curves
But what question about MATLAB are you asking? You have plotted the surface. and the level curves. And your code was correct to ...

9 days 前 | 0

已回答
Having -1 as part of the result when factoring a polynomial
You should understand that a factorization is not unique when you get down to a factor of -1. Yes, it may seem strange, but even...

9 days 前 | 0

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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...

11 days 前 | 0

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已回答
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...

11 days 前 | 0

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已回答
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...

12 days 前 | 0

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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,...

13 days 前 | 0

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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...

13 days 前 | 0

已回答
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...

13 days 前 | 0

已回答
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...

14 days 前 | 0

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已回答
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...

14 days 前 | 0

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