Community Profile # John D'Errico

### Retired

Last seen: Today 2006 年からアクティブ

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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Why DerivativeCheck would be allowed to be on while there is no GradObj?
You can set other options that will be ignored if they are not applicable. Would you rather have the code fail for no reason on ...

Finding the first index of a row where all integers of a defined list have occurred
Given a vector, can you simply find the first index where all have occurred? Just use ismember. x=randi([1,4],1,100) [~,locs] ...

How do I separate terms using symbolic expression?
Trying to get a symbolic tool to give you exactly the form you want to see is often terribly difficult, and usually not worth th...

Orthogonality by Singular value decomposition "svd"
Seems easy enough. A = randi(5,[5,3]) rank(A) So A is a simple matrix, with rank 3. There are 3 vectors that would form a bas...

How do I solve a linear optimization problem with a constrained output?
Seems easy enough. For example, suppose you have a linear programming problem where you solve it to minimize over x. But you al...

I want to check if something algebraically simplifies to 0 when i sub in values
syms q1 q2 q3 g Y u a rho e E=[q2,((q2^2)/q1)*(1-(g-1)*.5)+(g-1)*q3,((q3*q2)/q1)+(g-1)*((q3*q2)/q1)-.5*(g-1)*(q2^3/q1^2)]; Q=[...

How to convert a point in meshgrid to vector coordinates?
You already have the coordinates, so I'm not at all sure what your question asks. Perhaps an example would help. x = -10:5:10 ...

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'...

1日 前 | 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 ...

1日 前 | 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...

2日 前 | 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...

3日 前 | 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 ...

3日 前 | 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...

3日 前 | 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日 前 | 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...

4日 前 | 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...

4日 前 | 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...

5日 前 | 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...

5日 前 | 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 ...

5日 前 | 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...

5日 前 | 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...

6日 前 | 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....

6日 前 | 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日 前 | 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日 前 | 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日 前 | 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. ...

8日 前 | 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...

8日 前 | 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日 前 | 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...

9日 前 | 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...

9日 前 | 1