# 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**

what is the difference between assigning with and without range?

Yes. There is a difference, and a fundamental one. In the first case, the assignment a=b COMPLETELY replaces a. The variable is ...

etwa 6 Stunden ago | 0

Help solving a nonlinear function

I don't know what it means when you call something an equation that varies in a loop. This is certainly not a PHD level rabbit h...

4 Tage ago | 0

Solving for different thetas in an equation.

You CANNOT solve for both theta1 and theta2 in a single equation like that. (I assume you meant a single equation, because you h...

6 Tage ago | 0

How does this code support in carparking slot identification?

Out of context, this code is meaningless. It has absolutely nothing to do with the question you have asked about. And that was e...

6 Tage ago | 0

Project Euler: Problem 11

As far as why it failed test case #3, perhaps you need to write better, more efficient code. The code you wrote will be a bit of...

7 Tage ago | 0

| accepted

Integrate Acceleration to velocity, wrong plot

I would suggest your problem may be a simple one. When you integrate a function, there is a constant of integration, which is ...

7 Tage ago | 0

skewness and kurtosis of a weighted distribution

Sorry for being late to the party, but I had to answer this question once I saw an answer posted that does not actually help. T...

8 Tage ago | 1

WHAT IS THE SOLUTION FOR

Why? Is there a problem? Are you worried that your code is taking 1 millisecond longer to execute in this case? My point is, th...

10 Tage ago | 1

| accepted

FORTRAN POPPAR Equivalent in Matlab

The obvious answer is the simple answer... sum(dec2bin(I) - '0')

15 Tage ago | 0

| accepted

ode45 solving a differential equation that has no solution for given boundary conditions

So, you formulated a 2nd degree ODE. Converted it as: syms x(t) eqn = diff(x,2) + x == 0 [V] = odeToVectorField(eqn) M = m...

15 Tage ago | 0

| accepted

manually-written floor function code for rounding non-integers

If you want a mathematical expression, WRITTEN in MATLAB (where it will not have been written in the actual code) this could wor...

15 Tage ago | 2

| accepted

Questions on "Ordinary kriging"

As Jan told you, vstruct is provided by variogramfit. Where can you find that code? You need to download variogramfit, also prov...

15 Tage ago | 1

Rescaling curves by a factor to a single curve

You are looking to fit these curves using some nonlinear model. But you have not even said what model you want to use, just that...

16 Tage ago | 0

Can I solve a constrained optimization of general form of algebraic equation using matlab?

The problem is, even a simple function as you have written is is not as simple as you think. This is a problem of understanding ...

18 Tage ago | 0

| accepted

Problem when testing long decimal numbers

The problem is merely your understanding of floating point numbers and the methods used to store them. MATLAB uses only 52 bina...

19 Tage ago | 0

| accepted

Solving Ax=b but only for the values in some rows of x

We are given a problem where A is a large sparse matrix. We wish to compute the solution for the problem A*X == b where b ...

20 Tage ago | 1

| accepted

Optimization solvers change their performance in different programming languages?

No. The language makes NO choices. It does not prepare the problem differently. A language is not in itself sufficiently intelli...

20 Tage ago | 0

I have a problem with my code, it works fine but the results it isn't correct because the code is not compatible with the equations .. description below

This is one of those questions that tend to languish unanswered on the site. Why? Because you just say that your code does not w...

21 Tage ago | 0

how to create a vector A [1,1,2,2,3,3] from a vector B [1,2,3]

help repelem

22 Tage ago | 0

Lsqnonlin problem for calibrating accelerometer

Um, the solution is not to find Q. Because it is difficult to constrain a matrix to be positive definite. You don't want to try ...

22 Tage ago | 0

control the threshold of random numbers

You just say you want a distribution of numbers that is not uniform. But if you say only what it is not, that is not enough to s...

22 Tage ago | 0

| accepted

Find the transformation matrix

First, learn to use matrices, NOT numbered variables. Assuming that you have a matrix X, and a matrix Y, with x1 x2, y1, y2 as c...

22 Tage ago | 1

| accepted

how to solve 3 equations with a known variable and 3 unknown variables

The solution is simple, as I said, and somehow, I imagine you will end up changing the question again. I'll give you an answer, ...

23 Tage ago | 0

How can I identify the most important independent variable in an equation?

Is it possible? Not really. Not using MATLAB or anything else. You have ONE expression. You might describe the "most important" ...

23 Tage ago | 0

| accepted

Does Matlab have a library for Monte Carlo integration

Do they have a "library"? Not really what I would call a "library". Maybe you might. But why would they? They offer random numbe...

24 Tage ago | 0

How to get rid of small difference (or error) when I multiply 0.1?

You do understand that MATLAB, as is true of almost any programming language, uses binary storage methods to store all floating ...

29 Tage ago | 2

Masonry interpenetration issue in 2D simulation

What caused it? Since we cannot see code that you have not posted, my crystal ball is freaking out. It refuses to tell me anythi...

29 Tage ago | 0

Will there be an option in the future where Simscape or Simulink can solve PDE's?

Note that anyone who does know the answer to this is also under a non-disclosure agreement, so they could not tell you if they d...

29 Tage ago | 0

| accepted

How to draw perpendicular line from scatter points in 2-D plot

I would STRONGLY recommend you learn to use descriptive variable names. a? b? z? MATLAB does not charge more for you to use two...

29 Tage ago | 0

Solve function is unable to return the results of System of equations in the desired single number format instead of fraction ? help

Sure it is. You just need to convert the result from a fraction, into a floating point number. So either use double to create a ...

etwa ein Monat ago | 0

| accepted