Community Profile # John D'Errico

### Retired

Last seen: Today Active 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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Get a plot next to an existing plot
interparc is a function found on the file exchange (though written by me.) It is not part of MATLAB, until you get it from the f...

3 hours ago | 0

Prolate spheroid surface area
You need to learn about the dotted operators, and why they are necessary. Yuou want to compute an element-wise operation, one t...

10 hours ago | 0

how we write summation with loop
Note that I think you are trying to write some other language, while you are using MATLAB. For example, this is NOT legal MATLAB...

1 day ago | 0

Store trios of values from different vectors in an only vector
Please stop posting the same question multiple times. You made some effort though. First, learn to use meshgrid. [X,Y] = meshg...

3 days ago | 0

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I am trying to fit a line (to a blue curve in the image) using spline, pchip or makima function, however, theses function do not work properly (red line).
They don't work, because your curve does not describe a SINGLE valuesd function y(x). That is, for many values of x, there are T...

4 days ago | 0

How do I find the eigenvalues and vectors of an equation not of form (A*x = b*x)?
This is a classic problem in eigenvalues, caled the generalized eigenvalue problem. That is, if you want to solve the eigenprobl...

4 days ago | 0

How to convert decimals to Ascii characters?
The ascii encoding is not what you are asking to find, since this produces a different result. D = 0:63; char(D + 'A') Howeve...

5 days ago | 1

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Set of all bipartite graphs
No problem. Well, there probably IS a problem, as people are far too often surprised at how big things get. How do you generate...

5 days ago | 0

I have an image that is 234x432x4 size wise. I tried imshow() and image(), but it doesn't work. What do I use?
You have a 4 channel image, most likely CMYK, certainly not RGB. For example: imshow(rand(234,432,3)) As you can see, there ...

6 days ago | 0

3/8 Simpson's Rule
Please don't keep on posting the same question. You got no answer, since your question was itself terribly confusing, as was you...

6 days ago | 1

How to find position function with acceleration function using matlab
Just knowing the acceleration is meaningless, UNLESS you know how long the acceleration was in force. Next, acceleration is a ve...

7 days ago | 0

How can i get ODE to solve an equation if my y0 is more than one value?
You seem to have a misunderstanding. You are asking to solve a differential equation, here a first order ODE. (A Jan points out...

7 days ago | 1

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Get the displacement component which is perpendicular to the triangle (finite element)
A highly confusing question. You talk about a triangle, but you do not tell us the coordinates of the triangle, only the displac...

8 days ago | 1

Using nested FOR() loops to populate a matrix
You have a solution. It works. Do you need for loops, or worse, nested for loops? Of course not. The entire point of this answer...

9 days ago | 1

Why is it that when I am trying to create a function, the run button at the top turns grey?
You DON'T use run on a function. That makes no sense I'm afraid. Instead, functions in MATLAB are things you would call from ei...

11 days ago | 0

Matlab code for solving nonlinear equations
Actiiually, this is almost trivial. Seriously. It is. All of the trig terms are just known constants. And everything else is in ...

11 days ago | 1

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how to draw the hyperboloid of one sheet?
help fimplicit3

11 days ago | 0

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...

12 days ago | 1

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...

14 days ago | 0

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) +...

15 days ago | 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.

15 days ago | 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...

15 days ago | 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 ...

17 days ago | 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...

17 days ago | 1

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...

17 days ago | 0

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...

17 days ago | 3

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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...

20 days ago | 0

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.) ...

20 days ago | 1