# John D'Errico

### Retired

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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**Content Feed**

Upper bound curve that passes through the extreme (highest) points

I would argue a convex hull is probably at least close to what is wanted. That it works here because the envelope is roughly a c...

4 hours ago | 0

How to find number of bit change between binary numbers?

Read what @Jan said. xor followed by sum is the simple way to go, of course. And we really have not been given enough informatio...

14 hours ago | 1

infinity recursion with in the program

What do you expect? Look carefully at your code. I've extracted the only lines that matter below. function stabil = punktStabil...

15 hours ago | 0

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Most efficient way to solve a symbolic equation system with more than 2k unknowns

Symbolic solvers are SLOW. Well, comparatively so. This is partly because they use high precision. The computations, if they are...

1 day ago | 0

I want to ask how to define the partial fraction code single number located at the numerator?

Remember that MATLAB does not understand implicit multiplication. That is, 4x is not interpreted as 4*x. In MATLAB, 4x is just a...

1 day ago | 0

How to extrapolate the data while some data is already supplied on one spine?

Extrapolation using a spline (in any form)? A terribly bad idea in general. Extrapolation over a long distance? Another terribl...

1 day ago | 0

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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 ...

2 days ago | 0

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] ...

2 days ago | 0

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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...

2 days ago | 0

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...

2 days ago | 1

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...

2 days ago | 0

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=[...

2 days ago | 0

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 ...

3 days ago | 0

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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'...

3 days 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 ...

4 days 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...

4 days 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...

4 days 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 ...

4 days ago | 1

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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...

5 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...

5 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...

5 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...

6 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...

7 days ago | 0

dize ifadesi matlab'da yazılamaz

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...

7 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 ...

7 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...

7 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...

7 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....

8 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...

8 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...

8 days ago | 0