John D'Errico

Retired

Last seen: Today | Active since 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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Answered
How to solve multiple equation with several conditions in it?
Is chi known? If not, then chi is one of your unknowns, and it must be solved for. Regardless, there will be infinitely many sol...

23 hours ago | 0

Answered
case sensitivity issue of "load" function
You cannot change the behavior of existing supplied code. If it works that way, then it does, and there is no way to tell load t...

2 days ago | 0

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Answered
I need to input a matrix of size 2x2 which is something like this A= [ 1 - 1.8629z-1 + 0.8669z-2 , 0 ; 0 , 1 -1.8695z-1 + 0.8737z- 2 ] which is a 2x2 Matrix
So do it. What is the problem? If z is known, then just type it in, pretty much as written. Do you know how to raise a number ...

3 days ago | 0

Answered
MATLAB code of intersection
I answered exactly this question only recently. So your class must be all getting this homework assignment. https://www.mathwor...

3 days ago | 0

Answered
Is MATLAB 100% reliable? Do the users need to modify it according to their usage? I need this for my presentation in class. Thank you!
I'm sorry, but this question makes no sense at all. Define what you mean by "reliable" in this context. Are you asking if it wil...

3 days ago | 0

Answered
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 days ago | 0

Answered
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...

4 days ago | 0

Answered
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...

4 days ago | 0

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Answered
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 ...

5 days ago | 0

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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...

5 days ago | 0

Answered
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...

5 days ago | 0

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

6 days ago | 1

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Answered
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...

6 days ago | 0

Answered
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...

7 days ago | 0

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Answered
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...

7 days ago | 0

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Answered
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...

8 days ago | 0

Answered
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...

9 days ago | 0

Answered
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 ...

9 days ago | 0

Answered
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...

9 days ago | 0

Answered
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...

12 days ago | 0

Answered
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...

12 days ago | 0

Answered
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...

13 days ago | 0

Answered
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...

13 days ago | 0

Answered
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...

13 days ago | 1

Answered
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...

13 days ago | 2

Answered
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 ...

13 days ago | 0

Answered
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...

13 days ago | 0

Answered
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...

15 days ago | 0

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Answered
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...

15 days ago | 0

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Answered
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...

16 days ago | 0