Community Profile

# John D'Errico

### Retired

Last seen: Today 2006 年からアクティブ

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 to detect cluster of radial lines which are generated from same point ?
Surely there is a tool you can find in image processing to search for lines. Use it. Find all lines in the image. For EACH dark...

Symbolic solution for intersection points between a torus and a circle. How to make it concise? (for rewriting to C++).
How would I do it? Simple enoiucgh. The equation of a torus is easy to write in a parametric form, so as a function of two angle...

new interface for QR decomposition in Matlab 2022a
Yes. You are correct, in that QR now returns only the upper triangular factor. A = rand(5,3); result = qr(A) In the release h...

Polyfit coeffs weird output
You don't really need to show anything more than this: [p,s] = polyfit(x1,y,15); A degree 15 polynomial. That means the equati...

how to derivate an equation of x and y without taking any variable constant?
Specify that y is a function of x. You o so like this: syms y(x) Now you can differentiate that expression with respect to x. ...

1日 前 | 1

while loop keeps running forever
I think you seriously need to spend some time with the MATLAB tutorials. while is not terminated by endwhile A while loop is n...

1日 前 | 1

Power of a binary matrix
This is really pretty simple. Far simpler than you might think. You want to do a powermod operation, on a matrix, so mod(...

1日 前 | 1

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minkowskiSum
Compute the Minkowski sum of any two polygons or polyshapes, convex or concave.

3日 前 | ダウンロード 0 件 |

Generalized Minkowski Sum calculation
https://en.wikipedia.org/wiki/Minkowski_addition The convex case is quite simple to solve. I could write code for that in a few...

3日 前 | 2

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I need a graph to be smooth
You asked this question before. I answered it. In fact, you even show the code I wrote. And you accepted my answer then as I rec...

3日 前 | 0

Why does Matlab's divisors function take so long when working on an ordinary integer?
You ALWAYS. ALWAYS. ALWAYS need to consider the arguments for a function. Does it work in double precision, or as a sym? Don't f...

3日 前 | 0

boundry value third order problem
I don't know if this is homework. But it possibly is. So I'll just point you in a decent direction. And if you are going to sol...

4日 前 | 0

Normalizing a set of data to zero
Do you want ALL of those minima to be zero? If so, then you will need to do something especially artful. If all you want is the ...

4日 前 | 0

Random 3D Array of Cylinders with Random Rotation and Fixed Length
THERE IS NO SIMPLE SOLUTION. Accept that. For example, even for as simple a problem as random sphere packing, where you want to ...

5日 前 | 0

Why my polynomial function is wavy
A simple rule applies: Polynomials oscillate. Not infinitely many times. But this is a fundamental nature of polynomials. As the...

5日 前 | 0

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NEED URGENT HELP! Code keeps returning the desired variables as empty 0x1
Must a solution exist for all problems? No. Of course not. Those empty syms are a signal that MATLAB was unable to solve your pr...

5日 前 | 0

Trying to find area under my plot
You don't give your data. You show only a plot. So make a polyshape of it. Then compute the area. t = linspace(0,2*pi,50); x =...

5日 前 | 0

Replacing special character 'É' to 'E'
Easy peasy. str = 'ABCDEFGHIJKÉÉÀÀÄÄabcdefghijkl' strrep(str,'É','E') If there are other special characters you want replaced...

6日 前 | 0

Broad confidence bound range when fitting in Matlab
Wide confidence limits are typically a symptom, a reflection of uncertainty in some form. And unfortunately, we don't have your ...

6日 前 | 1

How to perform svd without using the inbuilt function?
Why? That is, why is SVD not acceptable? Yes, you could write a complete code to compute the SVD, without using a call to SVD. ...

7日 前 | 0

Why am I getting this error? "Array indices must be positive integers or logical values".
Is P0 a function? (NO. It is a scalar variable.) You have this: P_twitch_short(i) = P0(0.0258*(exp((stiff*RLS)))-0.0258); Did...

7日 前 | 1

How to recover jpg or RAW images?
I'd be looking at my backups. (A GREAT thing to do.) Of course, if you are asking this question, there are no backups. Before th...

7日 前 | 0

I need to smooth a 3d graph
x=1:10; y=1:21; z=[0 0 0 0 0 0 0 0 0 0; 0 0 0 0 0 -9 0 0 0 0; 0 0 0 0 -5 -7 0 0 0 0; 0 0 -10 -25 -15 -5 0 0 0 0; 0 -20 -32 -46...

7日 前 | 0

How i can solve the problem of primitive root?
What you mistake is that a and p are represented as DOUBLES. Can you compute a number as you want to do? What happens? a = 3; ...

7日 前 | 1

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Best way to solve this non-linear equation?
dsolve is not used to solve a PDE. It applies ONLY to an ODE or a system of ODEs. help dsolve There are no symbolic solvers in...

8日 前 | 0

Empty sym: 0-by-1
Don't write a whole mess of code, withput actually thinking about whether virtially the very first (significant) line you write ...

8日 前 | 0

simpsons 1/3 rule calculating error
Before you worry about how to plot things, and compute the error, should you worry if your code is correct at all? Gosh, that ju...

8日 前 | 1

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How find the function (equation) of the fitting surface using interpolation (method biharmonic)?
This question is asked hundreds of times on the site. The answer is, there is no simple "equation" you can write down. That is t...

8日 前 | 1

What distribution is appropriate for my data?
Why would you expect a distribution like that, with a strange hump on one side to have some predefined distribution that fits it...

8日 前 | 0

Plot two functions in one diagramm with different y-axis limits
Easy peasy. x = linspace(-5,5,1000); y1 = sin(x); y2 = cos(x); y2(y2 > 0) = NaN; plot(x,y1,'b-',x,y2,'r-') ylim([-1,1]) y...

9日 前 | 1

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