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John D'Errico


Retired

4.403 total contributions since 2006

Mainly retired from Eastman Kodak. (Of course, Kodak itself is now semi-retired. I don't think I had any influence in that.) I still write MATLAB code as I find something interesting, and I do attempt to write new tools to put on the File Exchange when I think I can make a contribution.

However, I DON'T answer direct e-mail questions, and I do NOT do homework. In general, your homework is YOUR problem, not mine. Please do NOT e-mail me with your homework problems or student projects. If I was willing to answer your questions, I would very rapidly become overwhelmed, because one question is never just one simple question.

When I'm not doing something with MATLAB, you might find me playing bridge, either in the club or online on BBO.

Professional Interests: MATLAB, numerical analysis, mathematical modeling

Avocational interests: Bridge, woodworking, woodturning

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Answered
When using alpha shape and the alpha radius is not specified. How does MATLAB obtain it? I want to understand it.
I don't have access to the code, so I can only surmise (since I've written alpha shape codes before in MATLAB, but not the one i...

etwa 13 Stunden ago | 0

Answered
intermediate exponential calculation goes to infinity
Calc 101. An integral is a linear operator. You can move any multiplicative constant inside or outside of the integral. Suppos...

etwa 19 Stunden ago | 0

Answered
Generate beta random number without statistics toolbox
As a followup, I note that the answer by dpb seems to be incorrect. There are several ways to generate a beta random variable. ...

2 Tage ago | 0

Answered
Symbolic solver yields wrong solution
It seems a subtle thing. We need to "branch" out from our preconceptions. ;-) pretty(solutions) / 0 \ | | | -p ...

2 Tage ago | 4

Answered
How do I explain the random functions to my professor?
I wonder if your professor needs to learn a few things. For starters, that Minitab is not doing anything any better than is MATL...

3 Tage ago | 5

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Answered
How to fit a curve to a step function?
ALWAYS plot everything. Do that before you do anything else. plot(xavg_40s1,havg_40s1,'.') grid on So your data looks like ...

3 Tage ago | 3

| accepted

Answered
Not enough input arguments
What is the purpose of that line? Lets see... help square 'square' requires Signal Processing Toolbox. So, assuming that you ...

3 Tage ago | 0

Answered
NAN from griddata for scatteredInterpolant
Your problem is that you have no idea how to use those tools. There is no need to use griddata AFTER you used scatteredInterpola...

3 Tage ago | 0

Answered
Graphing two parametric functions in terms of x
You got exactly the correct thing. You just need to look carefully at the y axis labels on the two plots. Just add this line af...

4 Tage ago | 0

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Answered
Are there any plans to add support in exportONNXNetwork tool for the maxUnpooling2dLayer?
Sorry, but surely not possible to tell you. MathWorks does not discuss their plans for the future on this forum. Anyone who doe...

4 Tage ago | 0

Answered
creating a curve from XYZ points (centreline) and then split curve into new points
This is a simple problem of interpolation, except that you don't know how to do the interpolation. Standard tools like interp1 d...

4 Tage ago | 1

Answered
Matlab Crushes when new .m file is added
This is not a crash, nor even a crush. It is just that MATLAB caches the files in the MATLAB directories. It does this to enhanc...

4 Tage ago | 0

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Answered
dot product for complex vector
help dot dot Vector dot product. C = dot(A,B) returns the scalar product of the vectors A and B. A and B must be ve...

5 Tage ago | 0

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Answered
i need to switch all integers in my array to positive numbers
You might need to read the getting started tutorials, if you are asking questions this basic. help abs

5 Tage ago | 0

Answered
large numbers in K means
x = rand(1048575,1); size(x) ans = 1048575 1 [IDX, C] = kmeans(x, 10); C Warning: Failed to converge...

5 Tage ago | 0

Answered
Expression of interpolating function
A high order interpolating polynomial is a REALLY, REALLY, REALLY bad idea. There, if i said it three times, it must be true. Se...

5 Tage ago | 0

Answered
In-Situ Combustion Model - MATLAB code
This is a simple error of syntax, which seems a bit strange for someone who has written such a long code to misunderstand. You s...

5 Tage ago | 1

| accepted

Answered
H is a 108x108 tall array, P is a 108x9 double array, when excute etu=H\P , this syntax is wrong, what is right ?
Why would you use tall on a problem that tiny? Anyway, you could just convert to double. In fact, that proves you do not seem to...

6 Tage ago | 0

Answered
Generate Random Matrix 0's,1's
Easy enough. matno = 10; % the number of random possiblities rows=10; columns=3; Now we want to create a matrix of size (row...

7 Tage ago | 1

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Answered
if i used a free trial will my files save
Yes.

8 Tage ago | 0

Answered
How do I extract 3D matrix from 5D matrix
What does it mean to extract a specific matrix? p = 1; z = 1; A = D(:,:,:,p,z); is a matrix of the desired size, extracting...

8 Tage ago | 2

| accepted

Answered
Sparse Matrix with Non-positive Indices
What you say makes no sense. If you have a full matrix already, and you are turning that into a sparse matrix, then you would ju...

9 Tage ago | 1

Answered
Problem optimizing anonymous function using fzero
There is no need to use symbolic tools to solve problems via fzero, merely understanding how to use functions. However, your que...

10 Tage ago | 1

Answered
error using Solve with inequality
You did not follow the example carefully. syms x >> S = solve(x^2 - 4*x + 3 < 0,'returnconditions',true) S = struct with ...

10 Tage ago | 1

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Answered
Obtain eigenvalue from matrix and known eigenvector
The simple answer, as long as the vector x IS an eigenvector. is just: val = norm(A*x)/norm(x); You should see that this is no...

11 Tage ago | 0

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Answered
fsolve doesn't give correct answer even with close initial guess
A serious issue is that you use many numbers accurate to only 2 decimal digits. So even though you may think the answer is corre...

11 Tage ago | 0

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Answered
nonlinear curve fitting a function on data
sin(theta) is not a variable name. beta = 1.135e-4; sintheta = [-0.81704 -0.67649 -0.83137 -0.73468 -0.66744 -0.43602 0.45368 ...

11 Tage ago | 1

| accepted

Answered
I have 30x30 matrix and need to extrapolate lower triangle numbers
You just want to extract the lower triangle, whatever is in it? The result going into a vector? A = magic(5) - 10 A = 7 ...

13 Tage ago | 0

| accepted

Answered
Solve for a system of equations
This is not actually a question about MATLAB. Why would you assume that every set of complicated nonlinear equations has an exp...

13 Tage ago | 0

Answered
Matrix Division: Different sized matrices
Is there a reason why you have not read the getting started tutorials? The manual is always a good thing to read. C = A./B; ...

14 Tage ago | 2

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