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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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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...

alrededor de 7 horas hace | 0

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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 ...

alrededor de 14 horas hace | 1

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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...

alrededor de 15 horas hace | 0

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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...

1 día hace | 0

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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...

2 días hace | 0

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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 ...

2 días hace | 0

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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 ...

3 días hace | 0

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Fastest possible prime number detection without using break or return
You did write working code to find primes. Well done there. But the fastest code? Without breaks, or returns. Easy peasy. Write...

4 días hace | 0

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I am new to matlab and I am trying to get prime numbers
But these loops will not result in prime numbers. (As you have found.) I think you are trying to do a simple sieve, or something...

4 días hace | 2

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How can i calculate the area under two curves that intersect?
1. Subtract the two curves. 2. Take the absolute value of the difference. 3. Compute the integral. Note that you ...

4 días hace | 1

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the arc using the chord
Your question is far too general, too vague to have an answer. There are infinitely many "arcs" that will pass through two poin...

4 días hace | 0

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MIL SIL equivalence check.
A literally impossible question to answer. Both far too broad, too vague, and yet extremely specific. It is not even clear what ...

5 días hace | 0

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How do I create a variable H which contains the product of 5 and the values of B in the 1st and 9th rows, and the 1st and 2nd column.
Ok, first, you do understand how to extract the elements from B. Good there. I think maybe the question wording is confusing you...

5 días hace | 1

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Is this a logical Error in Matlab ? exp (pi*i*6) = 1.000000000000000 - 0.000000000000001i. WHY an i component ?, should just be 1
Remember that pi in MATLAB is not truly pi, any more than pi is 3.14, or even 3.14159. pi is a transcendental number. There are ...

5 días hace | 2

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How can MATLAB's extensive suite of functions for data analysis and visualization be utilized to import, process, and analyze simulation data, including performing frequency a
Um, learn MATLAB. That means you need to learn how to read the help, the documentation for those tools. Start by doing the bas...

5 días hace | 0

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Symbolic integration has 3 solutions based on integration variable range, how to extract one of these?

7 días hace | 0

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How do I find the most stable N consecutive numbers?
The mean difference? What is that exactly? In terms of mathematics? Are you looking for the 50 element consecutive subset with ...

7 días hace | 0

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Possibly spurious solutions - Matlab blocked with no answers
You are attempting to solve for an analytical solution of 12 simultaneous nonlinear equations, in 12 unknowns. This, even if it ...

9 días hace | 1

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Solving goal programming problem with MATLAB
READ THE ERROR MESSAGE! What did it say? "Failure in initial user-supplied objective function evaluation. Optimization cannot c...

10 días hace | 0

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How to set an axis with arbitrary, but equally spaced, scaling.
You could not plot versus the numbers 0,1,2,3, but then set the x-tick labels as you wish? x = [1/3 1/2 1 inf]; xfake = [0 1 2...

11 días hace | 1

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All possible combinations of a matrix
Did you intend to write 1.024^13? This is not even an integer, and only a little larger than 1. 1.024^13 So there are 1.3611 u...

11 días hace | 1

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cubic spline interpolation - mixed boundary conditions possible?
You generally don't want to do this. That is, fit one spline, then construct a second spline to match the first. The result will...

12 días hace | 0

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what's the relation between A , B and M,G for this Nonlinear system of equation ?
This is not even remotely a question about MATLAB. As such, it should arguably not even be on Answers. But I have a minute to re...

14 días hace | 0

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Check code compatibility with older releases
A way to automatically check code compatibility with older releases, and see at what point a feature that you use makes your cod...

14 días hace | 0

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How to delay a signal using basic operators
This comes down to boundary conditions. So, first, a simple signal... x = [2 3 5 7 11]; Can't be any simpler than that. Now, s...

14 días hace | 0

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Generate an orthonormal matrix H mHxNh rank(H)=r
Seems trivial enough. Not possible, at least not for this case. But trivially not possible. mH=5; nH=3; r=2; So a 5x3 array, o...

14 días hace | 0

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What does the error message "input must be real and full" mean?
The gamma function requires a real input. Although I recall that the symbolic version of gamma can handle complex input. But the...

15 días hace | 0

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Mod or Modulus operator in MATLAB
Be careful, as if you look for mod or modulus, you will often see the functions mod or rem, which essentially compute a remainde...

15 días hace | 0

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Can a MATLAB home license be tied to a dongle?
You should contact customer support directly and ask your question. Answers is not that. Support may be able to offer an idea th...

16 días hace | 1