Community Profile # John D'Errico

### Retired

Last seen: Today 2006 이후 활성

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 draw the hyperboloid of one sheet?
help fimplicit3

약 2시간 전 | 0

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if and sum not working together
I'll say the same thing, but differently. As @Steven Lord points out, you cannot represent the fraction 1/3 exactly as a decim...

1일 전 | 1

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Looping if between 2 numbers
As @Jeffrey Clark said, the & operator is a LOGICAL operator. Perhaps what you want to do is have a loop over a discontigous dom...

3일 전 | 0

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How can I solve a system of non-linear equations with complex numbers?
WHY NOT TRY IT? Assuming you really intended for the second equation to use sind(120)... syms theta r eq1 = 0 == 2*cosd(240) +...

4일 전 | 0

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what formula do I have to put for calculating by using MATLAB?
Start here: help sum Then spend some time on the MATLAB Onramp tutorial, since this is a basic question.

4일 전 | 0

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Question about how the isosurface function works
isosurface cannot use interpolation? Why not? All that is necessary is the ability to perform LINEAR interpolation, between pair...

4일 전 | 0

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Extreme points of a polyhedral set
Was it really necessary to put a picture of the equations into your question, when simple text was just as easy? That means, in ...

5일 전 | 0

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How to approximate a multivariable arctan function?
@Sam Chak has suggested an interesting idea in a comment. However, while it is not a bad idea at first glance, I suspect it will...

6일 전 | 1

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Formatting of result values.
You cannot write it in that form, at least not easily. Yes, you could write a formatting code. But you would need to write it, s...

6일 전 | 0

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vectorized code is more time consuming than a simple for loop
It is not uncommon to have vectorized code be slower than a brute force loop. Why? The word "vectorization" can refer to many d...

6일 전 | 2

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Problem with non-linear implicit equation using fsolve
a = 1.5; R = 190; bmax = 0.0024139; bmin = 9.779e-10; Since you do not tell us the values of A and B, only the range, I'll...

9일 전 | 0

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How to sort points clockwise or counterclockwise?
Can you compute the polar coordinates angle, around that mean? (Hint: use atan2. Don't forget to subtract off the mean FIRST.) ...

9일 전 | 1

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Scaling variables for integration with ode15s
There is a reasonable chance your results may problematic, if you do not scale things. While you may get a result, you will have...

9일 전 | 0

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1, 4, 7, 2, 5, 8, 3, 6, 9 serie
Yes, @Tom has given a great answer. The way I would solve it on any normal day. But, just perhaps, is there another way? There a...

10일 전 | 0

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Sentiment Analysis Expand Contractions
Is it possible? Of course. Search for the possible contractions. Replace them with uncontracted forms. Note that SOME forms woul...

10일 전 | 1

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Converting system of equations to form Ax=b
help equationsToMatrix For example. syms x y E1 = x + y == 1 E2 = x - y == 2 [A,B] = equationsToMatrix(E1,E2,[x,y])

10일 전 | 2

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How to assign a symbolic matrix to another new matrix?
You are NOT assigning a symbolic matrix to another "new" matrix, but you are instead trying to stuff symbolic elements into an e...

11일 전 | 0

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Access contributor message threads on MATLAB Central
No. And, yes. Sort of. Is that a good answer? If the person you wanted to contact does not have messaging allowed, then you can...

11일 전 | 0

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I need to change this code into one that can solve complex roots
Interesting. It does not work? :) Gosh, You could have fooled me. I'll try an example. (I've attached the code you gave, so it w...

12일 전 | 0

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Creating sub arrays from a larger array
DON'T split them into separate, named arrays. This is just a bad way to write code. It will create buggy, slow code, even if you...

12일 전 | 0

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How to plot this implicit function? (It's one parameter also changes)
The vertical axis indicates the value of phi. F3 = @(x,y,phi) y.^4 + y.^2.*(2*x.*tan(phi)-1) + x.^2.*sec(phi).^2; fimplicit3...

13일 전 | 0

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How to find limit of a function
What you have written is NOT a sequence, but a function of one variable. If you are asking how to find the limit of that functio...

13일 전 | 0

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How to obtain an input-output relation for NN trainNetwork or similar functions
This is a common question, where someone wants to see a simple function they can write down and understand, from a complex tool....

13일 전 | 1

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How can i take the log2 of x plus 1 of a matrix
What function in MATLAB gives the log, with base 2? help log2 So what line of code would add 1 to x, and then take the log, ba...

14일 전 | 0

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Why ''int'' and ''integral'' return different answers
As others have said, the problem with integral is because of the singularities. Numerical methods don't like singularities. zzz...

14일 전 | 0

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How to implement a description for variables in the code?
So you want a tooltip to appear, hovering over each variable or line of code, but have no explicitly written comments in the cod...

15일 전 | 0

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Interpolation for 2 dependent output data
Trivial. You just have TWO interpolation problems. Interpolate output1 as a function of the input. Then interpolate output2, als...

15일 전 | 0

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In epsilon test for comparing equality of two numbers. How to improve the test?
Can you "improve" the test? What does improving it mean? How close do two numbers need to be considered the same? For example, ...

16일 전 | 0

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Combination of two values in a list to get the value of an input value
Easy, peasy. Yet, this is very possibly homework. Yet, you have already gotten an answer, that is pure brute force, when a far b...

16일 전 | 0

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convert equation to code
Your problem is that the cosine function produces only numbers between -1 and 1. That is another way of saying that acos ONLY wo...

16일 전 | 0