# John D'Errico

### Retired

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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**Content Feed**

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 ...

circa 11 ore fa | 0

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...

1 giorno fa | 0

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...

1 giorno fa | 1

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 ...

1 giorno fa | 1

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...

1 giorno fa | 0

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 ...

1 giorno fa | 0

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...

2 giorni fa | 1

| accettato

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 ...

3 giorni fa | 2

| accettato

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...

3 giorni fa | 0

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

Or do this: syms r umax Radius mom_2 = int((umax*(1-r/Radius)^(1/7))^2*2*pi*r,r,0,Radius) subs(mom_2,Radius,1) Note that it ...

4 giorni fa | 0

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 ...

4 giorni fa | 0

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 ...

7 giorni fa | 1

| accettato

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...

7 giorni fa | 0

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...

8 giorni fa | 1

| accettato

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...

8 giorni fa | 1

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...

9 giorni fa | 0

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...

11 giorni fa | 0

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...

11 giorni fa | 0

| accettato

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...

11 giorni fa | 0

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...

11 giorni fa | 0

| accettato

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...

12 giorni fa | 0

| accettato

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...

13 giorni fa | 0

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...

13 giorni fa | 1

| accettato

How to fix "Number of equations greater than number of indeterminates. Trying heuristics to reduce to square system." error.

You need to understand what was wrong in your forumulation. You want to solve this system using symbolic tools. % define some c...

14 giorni fa | 0

Jumps in roots finding solutions

Lets spend some time to understand what happens. Consider the simple polynomial: y = x^5 + 3*x^4 + (2+t)*x^2 - t^2*x + (1+...

14 giorni fa | 0

Solving system of nonlinear equations using Matlab

fsolve does not apply constraints. It does not know that you think some coefficient should be some number. It does not care. All...

14 giorni fa | 0

Newton Raphson implementation, not converging, maybe error in implementation

There are some significant misunderstandings on your part that I want to clear up, as well as perhaps help you solve your proble...

15 giorni fa | 0

| accettato

Progress bar takes lots of time

Yes, a waitbar takes time to update. It looks like you are calling it a lot. And every time, it does an update. And since this i...

16 giorni fa | 0

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Adoption of Name=Value in Function Calls what is best practice?

What is best practice? I kind of like the new syntax. But best practice would seem to be whatever you like. At some point, might...

16 giorni fa | 0

| accettato

Solving non linear inequalities in 2 variables

The "range of variables? Those inequalities will generally describe some nonlinear "thing", even if they describe a bounded doma...

16 giorni fa | 2

| accettato