Community Profile

photo

John D'Errico


Last seen: Today

Retired

5.297 total contributions since 2006

(Don't contact me. I won't answer questions.) A retired mathematician, numerical animalist, woodworker, bridge player.

Contact

John D'Errico's Badges

  • Master
  • Revival Level 3
  • 36 Month Streak
  • Quiz Master
  • Promoter
  • Speed Demon
  • 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
  • First Answer

View all

Contributions in
View by

Answered
how can I draw half circle in matlab ?
Sigh. You DID make an effort. It is not even a terrible solution, though what you did will not work, since it will at best be a ...

alrededor de 9 horas ago | 2

| accepted

Answered
linprog cannot find solution
While you claim a solution exists, initially, I sincerely wonder if it truly does. I may learn differently by the time I am done...

alrededor de 12 horas ago | 1

Answered
How to Run PSO with Real Data
You can't. That is, the optimal is just the optimal value at each point in your sample. You cannot do better than that, at least...

1 día ago | 0

Answered
How to solve for x in an sin equation?
No. There are INFINITELY many solutions. So you cannot say you want the OTHER solution. You can simply enough find a positive so...

2 días ago | 0

| accepted

Answered
linearly independent eigen vectors
And for some strange reason, you think that eig as applied to a diagonal matrix does not produce a set of independent eigenvecto...

3 días ago | 0

| accepted

Answered
How can large sparse matrix (Y bus matrix of order 800*800) be done inverse in Matlab?
An 800 by 800 matrix is barely what I would call large anymore. Perhaps 40 years ago, yes. Today, it is almost tiny. Ok, not tin...

3 días ago | 0

| accepted

Answered
How to subtract from a vector array and, if the answer is lees than 0, have it return a value of 0
Simple. No need to test anything either. Just use the max function. x = [1 2 3]; x(1) = max(x(1) - 2,0); x x = 0 ...

5 días ago | 0

Answered
Calculate factorial with 2 variables
Why do you feel you need to use loops? You should never write your own code for something that is far better computed using an e...

5 días ago | 2

Answered
Random number from 1 to 100 if the number between 20 to 30 add 100 if the number 50 to 60 minus 100.
I'll generate 10 samples. N = 10; X = randi(100,1,N); ind = (X >= 20) & (X <= 30); X(ind) = X(ind) + 100; ind = (X >= 5...

7 días ago | 0

Answered
Curve Fitting and Distribution Fitting
You have what, 13 data points? A model with many exponents in it? A model that is surely based on no real physical meaning of th...

10 días ago | 0

Answered
Integral of bessel function returns all zeros
It is a really bad idea to use gamma as a variable name because you are now stepping on the name of a very useful function in MA...

10 días ago | 0

| accepted

Answered
Sampling data using contraints
Use my randFixedLinearCombination tool, as found on the file exchange. (I did just post an update today, fixing a bug the code t...

10 días ago | 1

| accepted

Submitted


randFixedLinearCombination
Uniform random samples over a n-dimensional hyper-rectangle, subject to a linear equality constraint

10 días ago | 5 downloads |

Answered
recursive function to check a Palindrome
Why not try? I won't write it for you, as the entire problem is to make you think. I'll give you one hint, and I will hope nobod...

10 días ago | 1

Answered
Constructing a Maze with vectors
Insert NaNs between eack block of lines. X = [x,nan,x1,nan,x2]; Y = [y,nan,y1,nan,y2]; Now the various sets of line segments ...

10 días ago | 1

| accepted

Answered
How to solve exponential equations.
Thank you for posting this as a question instead of an answer. The simplest way to solve this is if you have the curve fitting ...

11 días ago | 0

Answered
creating a repeating diagonal matrix
You want to repeat that sequence on the main diagonal? v = [4 1 0 1]; A = diag(repmat(v,1,25)); That is, use repmat to replic...

13 días ago | 0

| accepted

Answered
Matrix equation solution keep giving only structure of the array not the value
As I explained in my comment to @Vasishta Bhargava, this is a problem with 3 equations, but only 2 unknowns. It is known as an o...

13 días ago | 1

Answered
CurveFit on Vector Data Points
The problem is, your data appears to be highly noisy. You can use simple linear interpolation to interpolate the data. KSSV hs ...

13 días ago | 0

Answered
Complex answer of acos function
The acos of a number that exceeds 1 or -1 is complex. This is the ONLY way that can happen, at least unless you have defined you...

13 días ago | 0

| accepted

Answered
How do I iterate if I have points from [-20,5,0] to [20,5,0]?
First, learn to use MATLAB as a matrix language. That often means not thinking in terms of loops. s_vector=[-20,5,0]; % line st...

13 días ago | 0

| accepted

Answered
If I take 10 points in a high resolution rectangular grid is there some code or some function in matlab that displays volumetric object.?
Is there some code that can automatically take some small set of points (worse, possibly with some noise? You did mention smoot...

14 días ago | 0

Answered
Multiple errors with derivative calculator code
This is not valid syntax in MATLAB. It may be so in some other language. But not so here. f() = str2func(['@(x)', 'g']); As yo...

15 días ago | 1

| accepted

Answered
Can you trust in Matlab exact arithmetics ?
Trust is a difficult thing. Blind trust is a bad idea, as if you do anything you want, you may be mis-using the tools. And if yo...

15 días ago | 0

Answered
How can I solve the set of liner equations using lsqlin?
IF it is ok to violate the sum to 1, then do as David has shown. The solution he wrote will allow that equation to be violated. ...

18 días ago | 0

| accepted

Answered
3/8 Simpson's Rule
First, learn the basic MATLAB functions. That is, exp is used as exp(x), not exp^x. The latter makes no sense in MATLAB. exp is ...

18 días ago | 0

Answered
simulate a dice throw
Why not? Remember that numbers are just symbols. It is how you choose to interpret those symbols that matters. If you want to as...

19 días ago | 0

Answered
Numerical Methods Backward Difference
I won't directly do your homework for you. I'll show you how you might solve for the coefficients of a formula you should alread...

19 días ago | 1

Answered
SVD of each row of a matrix
Sorry, but this seems to make little sense, since most of that set of singular value decompositions will be trivial. Or, perhaps...

20 días ago | 0

Answered
Matlab reads file with different order
Must I point out the data in that file are arranged as: data = textread('RQ_par.txt') data = 0.9011 ...

20 días ago | 0

Load more