Community Profile

photo

John D'Errico


Last seen: Today

Retired

5.747 total contributions since 2006

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.

Contact

John D'Errico's Badges

  • Revival Level 4
  • Master
  • 36 Month Streak
  • Quiz Master
  • Promoter
  • Speed Demon
  • Top Downloads 2020
  • Top Downloads 2019
  • Personal Best Downloads Level 5
  • Editor's Pick
  • First Review
  • 5-Star Galaxy Level 5
  • First Submission
  • Thankful Level 4
  • Knowledgeable Level 4

View all

Contributions in
View by

Answered
How to make a function that calculates many coefficients (>100) and reclaim them on many functions without having to return all these values?
Return a single struct that contains all of these variables as fields.

etwa 6 Stunden ago | 1

Answered
How to fit data to the partial differential equation for 1-D diffusion?
Ok. I had some time to look at your surface more closely, It does not fit that PDE. It cannot do so. Now that I have your data.....

etwa 20 Stunden ago | 0

Answered
How can I introduce constraints to the nature of solutions provided by a boundary value problem solver such as bvp4c or bvp5c?
The simple fix that treats the problem in a way that is arguably correct, is to NOT work directly in terms of concentration! Tha...

ein Tag ago | 0

Answered
Find the max of a vector recursive
This is a godawful problem to solve using recursive coding. Why? Suppose your vector has a million elements in it. Then this cod...

ein Tag ago | 0

| accepted

Answered
How to fix this error “Index exceeds the number of array elements (57)” while using minboundquad function
That code was written so long ago, I forgot I ever wrote it. But also, it was written in the days when the convex hull and trian...

3 Tage ago | 0

Answered
matrix calculation for matrix
Simple. One line. No for loop. Nothing hard. B = A(10:10:end,:);

5 Tage ago | 1

Answered
Why this function infinity loop
Because if your powers grow larger than 2^53-1 (i.e., flintmax), the number is no longer expressable exactly as an integer. All ...

7 Tage ago | 0

Answered
why ga does not respect upper bounds ?
Um, ub = [40 1e6 1e6 1e6 1e4 1e4 9000]; numel(ub) I can count, but I let MATLAB do it for me. As you should see, you posed o...

7 Tage ago | 1

| accepted

Answered
i which library can i find those two functions (h-plane and e-plane) ?
There is NO such library, because those are not legal function names in MATLAB. A dash is not legal in a name, in a function OR ...

8 Tage ago | 0

Answered
How to neatly or properly display the answers for simultaneous equations?
You may want to learn how to use the symbolic toolbox, which can display answers in a form you may want. A = [2 3 5; 3 4 7; 1 1...

8 Tage ago | 0

| accepted

Solved


Divisible by 2
This is the first problem in a set of "divisible by x" problems. You will be provided a number as a string and the function you ...

10 Tage ago

Answered
First order derivative using Curve Fitter (smoothing spline fit)
For example, we might try using the same fit, on some data where I know the answer. x = rand(100,1)*2*pi; y = sin(x) + randn(s...

11 Tage ago | 0

Answered
csv to .mat file
help csvread help save Perhaps you need to do the Onramp MATLAB tutorial?

12 Tage ago | 1

Answered
Optimize function wich only admits scalar input
FIRST, NEVER return a variable that has the same name as your function. That is a dangerously, recursively incestuous operation ...

12 Tage ago | 0

Answered
How to tell solver that symbols are matrices
A = sym('a',[2,2]) As you can see, A is a 2x2 matrix. B = rand(2,2); X = rand(2,2); Asol = solve(A*X == B,A) So now, for ...

12 Tage ago | 0

Answered
How to simplify this symbolic equation - nominator and denominator manipulation
I never did understand why people worry about making a symbolic tool give a result in a mathematically identical form, that happ...

13 Tage ago | 0

| accepted

Answered
Estimate area inside point cloud
As long as the curve is a sequence of points defining the perimeter and they are distinct, you can just compute the area using a...

13 Tage ago | 1

Answered
Graphing a polyfit function
DON'T USE A HIGH ORDER POLYNOMIAL! DON'T USE A HIGH ORDER POLYNOMIAL! DON'T USE A HIGH ORDER POLYNOMIAL! Do I need to say it ...

14 Tage ago | 0

Answered
natural cubic spline interpolation matlab
PLEASE DO NOT SEND ME E-MAIL ASKING FOR HELP. I ask people not to do this. (Note that for those people who might decide to do so...

14 Tage ago | 0

Answered
How can I show only the data from variable?
Use semi-colons at the end of those lines where you do not want to see all the crapola dumped to the command window.

17 Tage ago | 0

Answered
New Variables & Name in loop
Don't do it. https://www.mathworks.com/matlabcentral/answers/304528-tutorial-why-variables-should-not-be-named-dynamically-eval...

18 Tage ago | 1

Answered
How to select last digit of numbers and put it into a matrix?
Well, since you did write a fair amount of code, homework or not is irrelevant. There are some issues with your code however. ...

18 Tage ago | 0

| accepted

Answered
Real solutions to polynomials
When you use solve, remember that first of all, it will be impossible to find algebraic solutions to a general polynomial of deg...

20 Tage ago | 0

Answered
Why in a function an output argument isn't saved to workspace?
Suppose you use ANY MATLAB function? How does it work? For example... x = 1:5; Suppose you want to compute the mean of that ve...

20 Tage ago | 0

| accepted

Answered
Hilbert Matrix in least squares polynomial regression
Is A really a hilbert matrix? LOOK CAREFULLY AT WHAT YOU WRITE!!!!!!!!! In fact, A is not even a valid 3x3 matrix. If you fail ...

21 Tage ago | 1

Answered
Find a value in a matrix
help max Look at the SECOND argument returned from max.

23 Tage ago | 0

Answered
How to find solution using VPASOLVE
You have 2 variables, with 4 equations. vpasolve is NOT a tool that attmepts to solve a problem APPROXIMATELY. You cannot use vp...

24 Tage ago | 0

Answered
how can I solve this problem..
Um, what do you expect? syms theta0 x=90; g=9.81; v0=30; y0=1.8; y=1; th = -y+tan(theta0)*x-g*x^2/(2*v0^2*cos(theta0)^2)+y0; ...

24 Tage ago | 0

Answered
How to find the row and column for a value within a matrix [c] nearest or equal to 700.
Easy. And there would be many ways to do it. c = rand(5,5)*1000 [~,ind] = min(abs(c(:) - 700)) [rowind,colind] = ind2sub(size...

24 Tage ago | 0

| accepted

Answered
function for addition 2^16 modulo
Your numbers are in BINARY form, and you want to add modulo 2^16. The simplest solution is to convert to a decimal integer. I'l...

25 Tage ago | 0

Load more