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# John D'Errico

### Retired

5,587 total contributions since 2006

DON'T contact me. I won't answer questions. PERIOD. I don't do your homework. I won't do consulting. A retired mathematician, numerical analyst, woodworker, bridge player.

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How do I check the compatibility of legacy MATLAB 2012b code with new versions of MATLAB?
Sorry. There is no tool that will scan through your code and automatically tell you what parts will run or not, at least not bey...

8 hours ago | 0

Volume Segmenter App not available
This is almost certainly not a problem per se, except for people who have older releases of MATLAB, or who completely lack the I...

8 hours ago | 1

How to know if a minimum found with Global Search is actually the Global minimum?
Bjorn and Stephen should be encouraged to make their comments into Answers. But let me expand on what they have both said. The ...

12 hours ago | 1

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initial condition ODE45?
You cannot. That is to say, not directly. I suppose you could formulate it as a shooting method, in which case it becomes a nonl...

1 day ago | 0

A QR complexity question
(Good points made by Bruno. This answer tries to dive a little more deeply than Bruno spent the time to do, but I really don't c...

1 day ago | 2

Explanation of the following eval expression
Lol. Whoever wrote the code should learn to use MATLAB, as this is just an abuse of eval, for absolutely no good reason. For ex...

2 days ago | 2

simulate a markov chain including the absorbing state "death"
You won't always eventually die? While there are ways for that to not happen eventually, usually they are the plot of some movie...

2 days ago | 0

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Is this code efficient to generate the Lagrange polynomial?
Is your code efficient to generate something you should not be doing in the first place? Note that a Lagrange interpolating poly...

3 days ago | 0

Using fzero for intesection and "integral" for area calculation
g=@(x)exp((-x.^2)./2); h=@(x) x.^2-4.*x; x=linspace(-1,5,100); plot(x,g(x)); hold on plot(x,h(x)); You did that much cor...

4 days ago | 0

Guess for fsolve returns similar answer (heavily non-linear equations)
We don't see your equations. Almost certainly, they are pretty nasty looking. You tell us the exit flag was -2. That flag says ...

4 days ago | 1

How can I use symbolic variables while solving problems of MATLAB Cody?
I recall that Cody disallows the use of essentially all toolboxes. Symbolic variables are only active for you, IF you have the s...

5 days ago | 0

Obtained results are far from the specified objective function when using fmincon with a Multi-Start.
No numerical optimization that applies to a completely general nonlinear function will converge to the global soution regardless...

5 days ago | 1

your function is complex. But a complex variable is really TWO variables, bundled into one. In ths case, it appears the imaginar...

6 days ago | 1

Matrix multiplication accuracy problem
The Mathworks is NOT rounding numbers just to make your life difficult. They are not rounding numbers at all, at least not beyon...

6 days ago | 2

Trouble computing the factorial of a vector
No. Look CAREFULLY at that vector. Are they really zero? Or are they just relatively zero? F = factorial(1:50); F([1 2 48 49...

6 days ago | 1

Solve plane equation with 3 points and additional condition
This is actually pretty simple. I think you may be missing how simple it is. In three dimensions, 3 points determine a plane. T...

6 days ago | 1

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Dealing with numbers bigger than Realmax
No. Not using double precision numbers. That does not say you can do nothing. You can use the symbolic toolbox to compute the ...

7 days ago | 0

While loop with power.
This is the discrete logarithm problem. https://en.wikipedia.org/wiki/Discrete_logarithm#:~:text=Modular%20arithmetic.%20One%20...

8 days ago | 1

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How to pseude-randomize dataset with constraints
So, you want it random, but you don't really want it random, in a sort of vague, unspecified way. Can you do this in MATLAB? NO...

8 days ago | 0

How to calculate the volume of a segment of spherical cap intersected by a plane ?
I did suggest this scheme in my response to your question. And it seems pretty easy to do, so I am not sure where the problem li...

9 days ago | 0

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Array indices must be positive integers or logical values
The problem lies here: for i = 1:N za(i) = (z(i+1) - z(i-1))/(2*h); end When the loop starts out, what is i? i is 1, ri...

12 days ago | 0

Help fitting data to an implicit equation
My thought would be the lazy solution. If your model is: ((1-y)^(1-b)/y)=exp(-kt) then log the model. That is, we know tha...

12 days ago | 0

How can I interpolate between my original endpoints with cscvn?
I think you do not understand splines. (Not uncommon.) Splines have the property that they can produce results that lie outsid...

12 days ago | 0

Function fitting on a set of data points
What did you do wrong? It looks like Jon may be correct, in that you did not use the newly estimated set of parameters from the ...

13 days ago | 0

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Question About Number Format in MATLAB Command Window
These are numbers from the symbolic toolbox. That toolbox does not use the format tools to display numbers (though perhaps argua...

14 days ago | 1

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How to Use "Ask a Question" Section Correctly?
It looks like this is a (surely quickly fixed) bug in the site itself. They recently made some changes, allowing users to use ...

14 days ago | 1

Precision (decimal digits) are very low and digits(32) does not help.
Of course, asking for 32 or more digits of precision is a bit on the side of the ridiculous, when the numbers going into the com...

14 days ago | 0

15 days ago | 0

array and inverse tan
I think you do not unerstand MATLAB. I'd start with taking the Onramp tutorial. atand of what? atand is a FUNCTION. You need to...

16 days ago | 0

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