John D'Errico
Last seen: Today
Retired
5 368 total contributions since 2006(Don't contact me. I won't answer questions.) A retired mathematician, numerical animalist, woodworker, bridge player.
John D'Errico's Badges
Answer 10 questions that were unanswered for more than 30 days
Awarded to John D'Errico on 22 Jan 2018
Contribute at least one answer each month for 36 consecutive months
Awarded to John D'Errico on 20 Jul 2017
Obtain 50 solvers for a problem you have created
Awarded to John D'Errico on 10 Sep 2020
Like a problem or solution
Awarded to John D'Errico on 13 Oct 2016
Be the first to solve a problem
Awarded to John D'Errico on 28 Aug 2016
Top ten contributors with the most downloaded submissions
Awarded to John D'Errico on 02 Jan 2020
Your submissions were downloaded 1000 or more times in a month
Awarded to John D'Errico on 01 Nov 2019
Your submission is selected as "Pick of The Week"
Awarded to John D'Errico on 09 Oct 2019
Publish your first comment or rating
Awarded to John D'Errico on 09 Oct 2019
Your submissions received 25 five star ratings
Awarded to John D'Errico on 09 Oct 2019
Publish your first submission
Awarded to John D'Errico on 09 Oct 2019
Accept 50 answers given by other contributors
Awarded to John D'Errico on 20 Jul 2017
100 of your answers have been accepted
Awarded to John D'Errico on 20 Jul 2017
Provide your first answer ever to someone else's question
Awarded to John D'Errico on 20 Jul 2017
how I will check the Conditional statement task?
The obvious way is to use a switch construct. for i = 1:100 switch mod(i,5) case 0 case 1 case 2 c...
environ 3 heures ago | 0
| accepted
Variable precision arithmetic in ode45 and others?
Short answer - no. Long answer - nnnnoooooo. ODE45 uses only singles or doubles. Nothing symbolic. vpa is a symbolic tool.
environ 6 heures ago | 0
| accepted
Solving a nonlinear equation numerically
It looks as if you don't need to solve it numerically. syms x(t) xpp = diff(x,t,2) syms k dsolve(xpp + k*sin(x) == 0) dsolv...
environ 6 heures ago | 0
how can i aproximate /modify long numbers
It looks like you really need to understand floating point numbers. a=abs(2.6599-2.65987) It looks like 3e-5. But is it? Chan...
environ 7 heures ago | 2
| accepted
How Do I get an Invoice for my purchase?
Answers is not customer support. It is a user supported group, entirely voluntary. We have no access to anything concerning an i...
environ 13 heures ago | 0
exhaustive search algorithm Consept
The method you are using is comonly called a multi-start method. It is generally NOT an exhaustive search, although that depends...
environ 16 heures ago | 0
2010 won't activate
The odds are good that your new computer will not run that old a release. 2010 is pretty old as things go. Check the system requ...
2 jours ago | 0
How to work with a matrix close to singular in MATLAB ?
Sorry, but no magic exists. This is why numerical linear algebra exists as an area of mathematics, and why courses are taught in...
3 jours ago | 0
| accepted
How to solve 3 functions in 4 variables
What you show is NOT the answer. It is AN answer. 3 equations with 4 variables is called an underdetermined problem. There is ...
4 jours ago | 0
Error solving three equations in three unknowns
syms a b c Tan = -b - 2 == 0; Man = c + 1 == 0; Lan = a + b - 3*c - 1 == 0; [av,bv,cv] = solve(Tan,Man,Lan,a,b,c) This is a...
5 jours ago | 0
Numerical Approximation of Fisher Information Matrix
You cannot perform numerical differentiation? At the very least, you can use tools for numerical differentiation from my derives...
5 jours ago | 0
| accepted
Finding an analytical fit for a multi-dimensional function
Read again what Walter has said. There is much to learn for you. You might also look at some of what is found in this post, whi...
5 jours ago | 0
optimization with multivariable and constraint
Sorry, but this seems just plain silly. You are way overthinking things. The new point P3 lies at the midpoint of the straight ...
6 jours ago | 0
How to create a 6 dimension array in Matlab and store values in it
It very much depends on what you want to do with that data. But I think you are looking for a very inefficient way to store your...
6 jours ago | 0
| accepted
How to write the codes for this gamma function?
Easy, peasy. Although since you are using gamma as a FUNCTION, it is a REALLY bad idea to use beta, another closely related spec...
7 jours ago | 0
| accepted
identify lowercase letters, uppercase letters, numbers and spaces
help ismember
7 jours ago | 0
Recursive function to reverse a vector
Hmm. Suppose you strip off the last digit of the vector on each pass? Can you do that? You already know how to find the last ele...
9 jours ago | 0
| accepted
I want to make a recursive function that sums all the digits in a number
The "last" digit? A little ambiguously stated. In the number 12345, is 5 the last digit you are asking about? It looks like you...
9 jours ago | 0
| accepted
How can I interpolate a screw surface?
Is this a single valued function of x and y? Or x and z, y and z? No. Is this a function over some contiguous convex region in ...
9 jours ago | 0
Help with syms function. Unable to find explicit solution
Would you assume that every equation you write down hs an analytical solution? Why would you? T = 10; h = 20; g = -9.81; ...
11 jours ago | 0
| accepted
how to separate variables of f(x,y)?
In a completely general sense, if you do not know IF the functions can be separated, then no it is probably impossible to do for...
12 jours ago | 1
nonlinear equality constraint with symbolic variables
Numerical optimizers CANNOT use symbolic variables. That is, this is meaningless when using a tool like fmincon. syms t [1 16...
13 jours ago | 0
linear regression in log-log scale
Sadly, while I wish the fitting tool would fit your data on log scales if that is how the axes are set, it does not. (That has a...
13 jours ago | 0
Why multi objctive GA doesn't give identical answers?
First, many optimization problems have multiple solutions. Nonlinear problems often do. Second, there is no assurance that any ...
14 jours ago | 1
| accepted
New to Matlab - need help with rearranging equation
There was NO error returned. It was a WARNING, that while you want to find a solution, none could be found. There are many thing...
14 jours ago | 1
solve Equilibrium Position of Mass - Spring - Damped System
As Alan pointed out, you probably wanted to take the 2nd derivative of x there in your system, not the 20th derivative. The term...
15 jours ago | 0
How do I express coefficient x, y, z using a, b, c, P0?
You can want to do anything you want. But unless you have a magic wand, that often fails. Here, you have ONE equation (3) that...
16 jours ago | 1
| accepted
How to solve Ax=B with some knowns in x and B
This is a moderately complex question, because I'm not sure you fully appreciate the problem, and I am also sure this is not you...
16 jours ago | 0
Row of a Pascal's Triangle using recursion
Simplest is to use conv. In terms of your code, I have no idea what you think the line PascalRow(1) = 1; does, but it does not...
20 jours ago | 0
memory overflow with double factorial function
Recursive formulas like this always seem useful, but they are terrible in terms of coding, in terms of efficiency. You don't wan...
20 jours ago | 0
| accepted
Select a Web Site
Choose a web site to get translated content where available and see local events and offers. Based on your location, we recommend that you select: .
Select web siteYou can also select a web site from the following list:
Americas
- América Latina (Español)
- Canada (English)
- United States (English)
Europe
- Belgium (English)
- Denmark (English)
- Deutschland (Deutsch)
- España (Español)
- Finland (English)
- France (Français)
- Ireland (English)
- Italia (Italiano)
- Luxembourg (English)
- Netherlands (English)
- Norway (English)
- Österreich (Deutsch)
- Portugal (English)
- Sweden (English)
- Switzerland
- United Kingdom (English)