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# John D'Errico

### Retired

4.739 total contributions since 2006

Please don't contact me. I won't answer questions.

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Answered
Replace the empty output of find() by the closest element
You are trying to use the wrong tool (i.e., find) to solve this. Well, you could use find, I suppose, with some significant effo...

ongeveer 20 uur ago | 3

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Answered
Calc of mean and standard deviation
It should look like what photo? The mind reading toolbox has never gotten past beta testing state, and the copy I have is full o...

1 dag ago | 0

Answered
How do I obtain the derivatives after interp2 with the 'spline' option?
interp2 does not return derivative information at the interpolation points. If you want to generate that at some general interp...

2 dagen ago | 0

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fminsearch for fitting a function to experimental data
Even after you fix the problems in multiplication, let me look at your model and your data. syms c2 k12 k2e t fun = 120*c2*k12...

3 dagen ago | 0

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Symbolic solution trigonometric equation
Why not try it? syms a b c x >> xsol = solve(a*sin(b*x) + sin(c*x) == 0,x) Warning: Unable to find explicit solution. For opt...

4 dagen ago | 0

Answered
How do i calculate these 3 unknows in these Equations
Easy enough. syms a b c x y z EQ(1) = a^2 + b^2 + a*b == x^2; EQ(2) = b^2 + c^2 + b*c == y^2; EQ(3) = a^2 + c^2 + a*c == z^2...

4 dagen ago | 1

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Answered
How to create a best fit line for data with an aymptote?
It partly depends on your goal. Do you just want to best estimate the constant asymptote? Or, are you looking for some function ...

5 dagen ago | 0

Answered
selection of n disticnt vector
Easy enough. A = 1:10; index = randperm(10,6); a = A(index(1:3)); b = A(index(4:6)); Since randperm generates samples witho...

6 dagen ago | 0

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how do I write variance in percentage?
A percentage of what? Percentage always implies you are comparing one number to another. That is, suppose you have some variable...

6 dagen ago | 0

Answered
Can I update a toolbox without updating Matlab?
Short answer: No. Long answer: Nnnnnooooooooo. Why not? You can't do it, because then the versions would not be consistent. Ju...

6 dagen ago | 0

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Answered
Matlab implementation of AlphaZero
Now that I have some free time... I'm pretty sure the answer is no. Alphazero is a tool that was developed that could learn g...

7 dagen ago | 0

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scatter3 error i not understand
Hmm. It took me a minute to see what the answer was from the error that was generated. scatter3(X,Y,Z,P) Error using scatter3 ...

7 dagen ago | 1

Answered
How can I write a function for this
Use plotregion, found on the file echange. https://www.mathworks.com/matlabcentral/fileexchange/9261-plot-2d-3d-region Note th...

7 dagen ago | 0

Answered
Getting the linear portion of a non-linear curve
As is often the case on a question like this, you have been too vague for us to comprehensively understand what you do "have". (...

7 dagen ago | 2

Answered
rotating this curve 20degrees
I would normally ask why not try it yourself, but I realize there are some issues that can easily catch you here. H = plot(t,sd...

8 dagen ago | 2

Answered
Why 4.8/1.6 is not equal to 3?
While there has been a lot of good discussion in the other answer, let me add a few points. When you type 4.8 in MATLAB, does ...

10 dagen ago | 1

Answered
How can I solve linear equation system in parallel?
You already are doing that! That is, decomposition uses all of the cores you have available for large problems. Watching my ac...

11 dagen ago | 1

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Answered
How can I get confidence intervals when the Jacobian matrix has an almost zero vector?
This is probably not a failure of the assumption of Gaussian arrors, though that may indeed be the case too. I cannot know. Wha...

11 dagen ago | 0

Answered
Can I run MAtLab on mac
Yes. Apparently so. https://www.mathworks.com/support/requirements/matlab-system-requirements.html

11 dagen ago | 0

Answered
Fit a conic section without mirror image hyperbola
This goes back to basic algebra. When does a conic section describe an ellipse versus a hyperbola? https://en.wikipedia.org/wik...

11 dagen ago | 0

Answered
Distance between points of a 3D centreline
Why not try diff? For example, what does diff(CL,[],1) do? TRY IT! What is distance? Does that give you something you might b...

13 dagen ago | 0

Answered
Signal into tolerance range - Comparison algorithm
It is often the case when my answer wants to be both no and yes. That is, no, there is no direct tool that does what you seem to...

13 dagen ago | 0

Answered
How to graphically represent the global minimum of an optimization problem with more than two variables?
Do you have a multi-dimensional holographic monitor? Yes, I know, this will not be invented for many years if ever, but that is ...

14 dagen ago | 0

Answered
Fast method to find average pairwise distance of a very large matrix?
You cannot compute the 100 billion pairwise distances, because the matrix won't fit in memeory. (Ok, symmetry reduces it to be o...

14 dagen ago | 0

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Answered
How to get multiple outputs from a function?
[x,y] = subfuntest(a,b); When you call it with no arguments, it returns only the first, putting it in the default variable name...

15 dagen ago | 1

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Answered
how to find the sum of rows in an array, that fit a condition?
When a problem is too complex to solve, then break it down into SMALLER parts, that you can handle. You want to know how many r...

15 dagen ago | 1

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Answered
Normal Distribution Specifying parameters
Hint: What does normcdf tell you? (In fact, I think this totally gives the answer away, IF you understand what the CDF means.) ...

16 dagen ago | 0

Answered
Solve equationsystem (A*V).'*B*(A*V)=C for matrix A
As it turns out though, your problem is actually quite simple. Assume that V is full rank. As long as that is true, then as can...

17 dagen ago | 0

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Answered
Does the cubic Hermite spline interpolation of a monotone data with known slopes guarantee the monotonicity in interpolation segments?
pchip always gaurantees a monotonic interpolant if the data is itself monotone. However... If you provide the derivatives yours...

17 dagen ago | 0

Answered
MATLAB equivalent to ls -l
It depends on what you want from it. What exactly are you looking for? D = dir MAY give you much of what you may want, if you ...

17 dagen ago | 0

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