# John D'Errico

### Retired

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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**Content Feed**

Acceleration at the center of the triangle

If you have some known parameter at the three corners of a triangle, then the best estimator of that parameter at the center of ...

7 hours ago | 1

How to use bitn

You cannot define a scalar variable as a binary one with an arbitrary number of bits. You can define integer variables, with a s...

2 days ago | 0

Why I'm getting error (too many arguments) in my integral

You need to pay MUCH more attention to your code. For example, just a quick look shows this: Intdoble6=int(int(2*y^2,x,0,1)4*x...

2 days ago | 0

I nee to write a code to solve a definite integral. The output format has to be fprintf.

Do you understand that MATLAB REQUIRES a multiplication operator? You cannot just put a number next to a letter, and expect MATL...

3 days ago | 1

Maximum Likelihood Estimation function

Is there another way? Why not negate the function, and then use a tool like fminbnd? Or fminsearch. Or fmincon or fminunc, or .....

4 days ago | 0

What optimizer should I use?

This is not a problem of finding an optimizer. This is a problem of understanding how to formulate a problem so that it is possi...

5 days ago | 0

simulation stopped because of step size tolerance and constraints

Let me see. You posed an optimization problem. The solver returned a result, one that SATISFIES the tolerances you posed. You we...

5 days ago | 0

Revolving a curve about the y-axis to generate a 3D surface

Certainly. Just write the code yourself. Seriously, it is not difficult. Consider the function y = f(x). f = @(x) x.*(1-x); ...

5 days ago | 0

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matlab rank of a matrix

Because the call: R = ones(100,100); rank(R,1e-20) attempts to do something that is demonstrably silly, in terms of double pr...

5 days ago | 0

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which project of these projects will be easy with matlab?

I think you do not understand. ANY project can be either easy, or too difficult for you to handle. What matters is if you unders...

10 days ago | 0

How should I approach solving differential equation as function of two variables r, k?

While you COULD use an ODE solver, this is something you would ONLY do if the ODE had no analytical solution. And this ODE has a...

10 days ago | 1

Fmincon too many input arguments

How are you using it? That is, how did you call the function try_no_gradient(u0)? When you get an error message, show the COMPL...

11 days ago | 0

How to subtract only certain elements of a vector

a and b are not vectors in your question, they are arrays. However, if you want to do this, nothing stops you from selecting th...

11 days ago | 0

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Plot the graph using non linear equation

A nonlinear problem like this is called an implicit function. You can think of the value of h, as a function of theta, but there...

11 days ago | 1

convert current date and time to char

Easier than you think. First, what is the current time? format long g CurrentTime = now That might not seem terribly helpfu...

12 days ago | 1

Ｌｉｍｉｔ ａｎｇｌｅ ｉｎ ［－９０，９０］ ｄｅｇｒｅｅ

You cannot simply constrain an ODE solver to stay within bounds. However, almost certainly, if the ODE solver wants to go outsid...

14 days ago | 0

Code involving factorials and a given value

Now that you have a looped solution, let me show how to solve the problem more directly. There are actually several solutions I ...

15 days ago | 1

how to solve this differential equation system symbolically?

This seems like a homework problem. But Walter has already given an answer, that I think is not helpful, since dsolve will fail ...

15 days ago | 0

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Optimization to find a deterministic number

Huh? This question is pretty confusing. But let me see where it goes. First, it seems you claim that g(x) is the solution of an...

16 days ago | 0

How to rotate about an axis parallel to x axis?

Simple. Effectively, you transform the problem to a rotation around the x axis, then after the rotation, you tranform back. For...

18 days ago | 1

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Matrix from measured data is singular, what could be the reason?

In no place in this thread have I seen the matrix A. I've seen various versions of it however, with various numbers of rows. I'v...

18 days ago | 0

Reinforcement Learning toolbox missing functions

If you have a current version of that toolbox, it should have those tools. which rlDiscreteCategoricalActor which rlValueFunct...

19 days ago | 0

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Calculate the distance between points in a large data set

LEARN TO USE MATLAB. Do not create numbered and named variables. DO create vectors and arrays. Use them. Since all you have pos...

20 days ago | 1

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Optimization terminated: average change in the fitness value less than options.FunctionTolerance.

Star has answered your uestion. However, I want to expand on what was said there. Too often, I see people confused by this messa...

21 days ago | 0

Describe non-convex region with linear inequality constraints

Nothing stops you from dissecting a polygonal region into triangles, even if not convex. As Matt said, you CANNOT use a set of l...

21 days ago | 0

How to find area of enclosed region (i.e., calculate Green's Theorem) in MATLAB?

You have a sequence of points in a loop. Create a potyshape from them, then compute the area. help polyshape methods polyshape...

22 days ago | 0

How to find matrix S, given by this equation

There is no unique solution. Or, there may be no solution at all. This looks vaguely like an algebraic Riccati equation. Your p...

22 days ago | 0

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Random Numbers from Stationary Distribution

Simpler to accomplish than others have said. But first, do NOT define those probabilities as separate variables!!!!!!!!!!!!!!!!!...

23 days ago | 0

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Vpa conversion of whole file

I'm sorry. You cannot now convert those files automatically, to take lines like a = 5; And automatically have MATLAB see thos...

24 days ago | 0

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Fitting line to a curve

Easy. Use findpeaks, to locate the sequence of points that represent the successive maxima of the curve. Use an interpolatin...

25 days ago | 0

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