John D'Errico

Retired

Last seen: Today | Active since 2006

Followers: 23 Following: 0

Message

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.

Statistics

All

View badges

Feeds

Answered
part 3 example was wrong
Answers is not official MATLAB support. So telling us a problem exists does nothing. Contact support directly. https://www.ma...

6 hours ago | 1

Answered
I'm trying to find solutions to variables in a system of non linear eqations, that represent a geometrical puzzle.
A problem is, we don't actually know what is the geometric system you are trying to solve, nor have you told us the solution you...

1 day ago | 0

Answered
Integrating a very long expression containing symbolic values
Is there some law of mathematics that everything you can or will write down has a solution? (No.) That int did not find a soluti...

2 days ago | 0

Answered
Can someone help me fix my bisection function?
Good code. Well, at least in terms of the documentation. Excellent in that respect. Readable code is important when you need to ...

2 days ago | 0

Answered
What is the interpolation algorithm behind MATLAB’s pcolor with FaceColor = 'interp' that creates sharp, defined boundaries？
There are three simple ways to interpolate inside a 2-d rectangular region. But two of them are analogues of each other. First,...

2 days ago | 0

Answered
How to compute the characteristic equation given the eigenvalues?
You have not asked this question as if it is a homework assignment, so I'll give an answer. The characteristic equation GIVEN e...

4 days ago | 0

| accepted

Answered
How to download old version of toolbox?
You cannot. That is, you cannot use an old toolbox for a previous release in a newer release of MATLAB. So what can you do? You...

5 days ago | 0

Answered
Bug with large HEX numbers
H = 'fffffffffffffffffffffffffffffffebaaedce6af48a03bbfd25e8cd0364141'; numel(H) So 64 hex digits, which would yield an intege...

5 days ago | 1

Answered
How to get consistant results when testing code performance
A single time test will be susceptible to anything that attracts the attention of your CPU. And sadly, your CPU suffers from com...

6 days ago | 0

Answered
update guess in fsolve
Um, no, You cannot always find a way to "update" your initial guess for fsolve. One can even prove this to be true. You can cha...

7 days ago | 1

Answered
How to remove columns in very large matrices.
GET MORE RAM!!!!!!!!! RAM IS CHEAP!!!!!!!! Need I say it again? You have a quite large array. (1.75e6*2000*8)/1e9 That arra...

8 days ago | 1

Answered
using sparse matrix and vpa function simultaneously
I wanted a nice bright red Lambo for Christmas. Nope. Did not happen, nor was it ever going to happen. The same applies to you. ...

8 days ago | 0

| accepted

Answered
Matrix is singular to working precision
I don't even need to run your code, to see an obvious mistake. In fact, I knew what I expect to be a problem, even before I look...

11 days ago | 0

Answered
real and integer variables
No. We won't do what is surely your homework assignment. But why not TRY IT! First, plotting it is trivial. LEARN TO USE a tool...

18 days ago | 0

Answered
Why matlab is not as intelligent as python
Why? Why is anything the case? Because it is. Because they are two different languages, with different capabilities, and differe...

20 days ago | 3

Answered
Matlab sparse matrix does not come out as I would expect
S=sparse([1 3 2 1 4],[3 1 4 1 4],[1 2 3 4 5],4,4) full(S) It works just fine. What did you do wrong? LOOK CAREFULLY AT WHAT Y...

20 days ago | 1

| accepted

Answered
defining upper and lower limits of a matrix
Is there any way to set the min and/or maximum values of the elements in a matrix, and do so automatically? NO. Well, not withou...

26 days ago | 1

Answered
how to optimize block toeplitz matrix ?
The one thing you NEVER, EVER, EVER want to do is stuff the elements into a sparse array iteratively. NEVER DO THAT!!!!!!!!!!!!!...

27 days ago | 0

| accepted

Answered
PC specs for heavy & complex simulations
No computer will ever be as fast as you want it to be. Even if you do get the fastest, most powerful computer you can possibly ...

28 days ago | 0

Answered
Which statistic is minimized in curve fitting app
The sum of squares of the residuals is mimimized. SSE effectively stands for Sum of Squares of Errors. What is the 2-norm? Just...

28 days ago | 1

Answered
I need to draw a shape in matlab help me
This is not a difficult problem. Not at all. But it is impossible for us to do it, based on having been given no information exc...

28 days ago | 0

Answered
Simmetrical Constraints in Multivariate Regression
Now please stop asking this question. I already suggested 3 ways you MIGHT solve it, the first time you asked. You could have ad...

29 days ago | 0

| accepted

Answered
Find limits satisfying a condition on an integral
You have posed a interesting problem, with a subtle flaw that possibly you don't understand. You asked to find an integral limi...

30 days ago | 0

Answered
Simmetry constraints in multivariate regression.
Sure. In fact, I can think of at least 3 ways to do so, almost trivially. Just estimate the upper (or lower half) of the matrix...

1 month ago | 1

Answered
how to find curve fiitng equation through custom equation
You can't. Yes, I want world peace. But do you think that just wanting it is sufficient? Nothing I do will change it either. The...

1 month ago | 0

Answered
Accidental deletion of project, how to contact file exchange admin
Why did you do that? Silly question, I know. ;-) Yes, it should be undoable. I'll contact the FEX admin and ask them to resolve...

1 month ago | 0

| accepted

Answered
Complex multiplication giving incorrect result
Yet another person who does not understand the realities of double precision arithmetic. Note that the imaginary part is roughl...

1 month ago | 2

Answered
What is the best kind of MATLAB function to teach beginners?
I think I agree with @Stephen23, in that teaching symbolics first can cause issues. We see many new users who think everything s...

1 month ago | 1

| accepted

Answered
Different results of the same caculation by loop code and by array code
As is almost always the case, when we see this complaint, it is because you do not understand how arithmetic works in terms of d...

1 month ago | 0

Answered
我买了学生版
Are you sure you have the student edition, and not the 30-day free trial? It would appear you have gotten the trial version, by ...

1 month ago | 0

John D'Errico

Retired

Statistics

MATLAB Answers

MATLAB Answers

Cody

Cody

File Exchange

File Exchange

File Exchange

File Exchange

File Exchange

MATLAB Answers

File Exchange

File Exchange

Feeds