# 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**

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'...

ongeveer 14 uur 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 ...

ongeveer 19 uur 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 dag 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 dag ago | 0

| accepted

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 ...

1 dag ago | 0

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 dagen 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 dagen 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 dagen 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 dagen 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 dagen 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...

4 dagen 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 dagen 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 dagen ago | 1

| accepted

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 dagen ago | 0

| accepted

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 dagen ago | 1

| accepted

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...

5 dagen 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 dagen 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 dagen ago | 0

| accepted

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 dagen ago | 2

| accepted

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 dagen 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...

7 dagen 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 dagen 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 dagen 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 dagen ago | 1

| accepted

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 dagen ago | 0

| accepted

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 dagen 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 dagen 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 dagen ago | 1

| accepted

ans = Empty sym: 0-by-1 error in solving equation

So many times I see this mistake made. I can understand where it comes from. But it gets MATLAB (actually solve) confused. When...

9 dagen ago | 0

Faster than pdist for cityblock on integers?

This issue is surely not a problem with the distance computation as anything complicated, as much as it would be generating and ...

10 dagen ago | 1

| accepted