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# John D'Errico

### Retired

Last seen: 1 day ago Active since 2006

DON'T contact me, as too many students then decide I am their personal consultant if I allow it. Anyway. I won't answer questions. PERIOD. I don't do your homework. I won't do consulting by mail. A retired mathematician, numerical analyst, woodworker, bridge player.

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How can I access the following builtin function code? [L,p] = chol(A,'lower')
Easy. Get a job at The MathWorks. If that is not an option for you, then sorry, you don't get to see the source code. They don'...

17 hours ago | 0

Optimising Limits of Chain integrals
I can't imagine why you want to do this. BUT, it is an interesting problem, so I'll take a look. Assume that all functions are ...

22 hours ago | 0

How to calculate the symbolic integration of rational functions?
If the polynomial has a sufficiently low degree, it can always be factored, in which case as has been pointed out, you just turn...

1 day ago | 1

pos function does not work
Now that we see what is meant by pos, we see that in fact, pos is just an array. It is not a function at all. https://in.mathw...

1 day ago | 0

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Pipe elbow creation using MATLAB code
What is not working? Why do you think it is not working? I would conjecture that one problem you have is you cannot model a 90 ...

2 days ago | 1

plot using matlab(parabolic)
It IS curved, though not truly parabolic. A parabola means something specific about the shape, as a polynomial curve. But you ju...

2 days ago | 0

Creating equal lists by minimizing variance on two factors
Why should there be such a function? My guess would be you want to use a tool like kmeans, clustering your data in 2 dimensions...

3 days ago | 0

pos function does not work
which pos We cannot tell you how to use a function that does not exist in MATLAB. Is pos a function that would be found on the...

3 days ago | 0

Find integral upper limit knowing the result and having an array
A basic rule is, you CANNOT use integral OR fzero with data, thus a vector of numbers. You CAN approximate your data using a fu...

3 days ago | 0

Optimal routing for building feeders in the form of a radial network
You probably need to use tools from graph theory. And there are a nice set of such tools in MATLAB. help graph help minspantre...

4 days ago | 0

Sure it does. S = "Hellow World" However, it is likely that you have an older release of MATLAB, which may not allow the use o...

4 days ago | 0

MATLAB error using fzero function
You cannot use fzero on a vector. A vector of elements is NOT a function. It is just a list of numbers. And while you may think ...

4 days ago | 0

Use of fmincon with objective function as m-file
Easy enough. The simple way, assuming all of the variables: {O_plus,O_minus,L_a,L_c,I_app,t} are defined in your workspace, is t...

4 days ago | 1

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Finding the maximum value in a single
The max function did not work? Why not? Surely you tried it? S = rand([1,128,3],'single') Smax = max(S,[],2) If you don't lik...

5 days ago | 0

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how can I write this in a compact form? can anyone suggest a single line code for it
At its heart, this is just a basic circulant matrix. So use a tool that will do that. I posted such a tool on the file exchange....

5 days ago | 1

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I want a graphical way to select/deselect points from a curve.
I posted this code on the file exchange many years ago https://www.mathworks.com/matlabcentral/fileexchange/13857-graphical-dat...

6 days ago | 0

Persistent variables when passing a matrix through a function
Yes, there is. By passing the elements of x in sequentially to myfunction. But then, you already learned that. Or, since myfunc...

6 days ago | 0

2D-surface in 3d space from points without relationship
This is less than a simple problem if you give no information at all about the surface in question. If it is a single valued thi...

6 days ago | 0

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How can I use the Genetic Algorithm (GA) to minimize a cost function of two variables C(T,K) where T is a real an K an integer.
Trivial. Write your function as an objective function. I won't do that for you, but just start at the beginning and write it. ...

7 days ago | 2

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how to solve the following equation by using Matlab
Your problem is: f = @(z) (0.10-0.3i)*z.^(-1) + (0.2121 - 0.0008i)*z.^(-2) +(0.9+0.001i)*z.^(-3); Please don't use curly brace...

7 days ago | 0

Plot sinusoid equation of x(t)
Do not define a variable with the names: sqrt, exp, real, imag, plot If you do, then what do you think will happen when you the...

8 days ago | 0

Yapay sinir aglari ile satis tahmini problemi cozdugumde R2 degerinin negatif cikmasi ne ifade ediyor. R2 degeri hangi aralikta olmalidir?
Let me give an example. x = rand(100,1); y = 5 - 3*x + randn(size(x)); plot(x,y,'o') First, fit a LINEAR polynomial model t...

8 days ago | 0

Can we get functions from the curve fitting toolbox?
New users of splines ask this question so many times. I can understand the question. But a spline fit is not a simple thing wher...

8 days ago | 1

matlabFunction: Why the extra ".0" and why only sometimes?
Does it really, really, really matter? Actually, there is a (subtle) reason for the 2.0. You should recognize there is some pot...

9 days ago | 1

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My code does does not go through the the if section
Rule # 1: NEVER test for exact equality of floating point numbers. (At least unless you fully, completely absolutely understand ...

9 days ago | 0

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Linearize an exponential curve for feeding it in GAMS
What do you mean by linearizing a nonlinear curve? I can think of many ways to do that. But no matter what, a nonlinear function...

9 days ago | 0

How to find fit for function with exponential and oscillation term?
Why is it not working? First, you NEED good startign values. ALWAYS. Whenever you have exponential models and trig models. What ...

9 days ago | 0

Missing function from Computer Vision Toolbox
I would first look at the release notes for R2022b, here: https://www.mathworks.com/help/driving/release-notes.html But, perha...

9 days ago | 1

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