Community Profile

photo

John D'Errico


Last seen: Today

Retired

5 140 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
  • Promoter
  • Speed Demon
  • CUP Challenge Master
  • 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 to measure the correct circularity??
It would not be unusual for that measure to exceeds 1. For example, given a circle, we would have a perimeter of 2*pi*r. So perm...

ungefär 8 timmar ago | 0

Answered
Fitting an exponential using nlinfit
Most of the code you posted is meaningless, since you save only the variables whos Name Size Bytes ...

ungefär 14 timmar ago | 0

Answered
random integer condition selection
You want to generate a random number of random numbers? With an additional constraint that all are greater than 0.5? This is far...

ungefär 20 timmar ago | 1

Answered
[Solved] Upsampling multidimensional array with interpn
That is NOT a 5 dimensional array. While you may THINK of it as a set of points that live in 5 dimensions, it is NOT a 5-d arra...

en dag ago | 0

| accepted

Answered
Plotting a function (Horner Schema)
While polynomic psychological analysis seems well beyond my talents, Horner's rule is pretty easy. :) And since you made a credi...

en dag ago | 1

| accepted

Answered
Matlab says the matrix is not symmetric
D = rand(100); D = (D + D.')/2; issymmetric(D) ans = logical 1

en dag ago | 1

| accepted

Answered
how can i create a circle with a face color changing radially
[x,y] = meshgrid(linspace(-3,3)); z = exp(-x.^2 - y.^2); H = pcolor(z); H.LineStyle = 'none'; colormap(jet) axis equal ...

en dag ago | 0

| accepted

Answered
Fit a curve on scatter data (main behaviuor)
You "want" the green line. I want the Buffalo Bills to win the Super bowl. Probably not gonna happen in either case. ;-) You wa...

en dag ago | 0

Answered
How can I understand why certain sets of random variates lead to the warning message "Unable to meet integration tolerances without reducing the step size below the smallest value allowed (1.136868e-13) at time t=51"?
Nobody yet wants to explain it? The standard reason for this error is because you are creating a problem that is too stiff for ...

en dag ago | 2

| accepted

Answered
What am I getting wrong with trying to create a sphere mesh using a golden spiral?
So you are not looking for a mesh at all, just a uniform sampling? Simplest might be to use a random sampling, with a twist. Tha...

2 dagar ago | 0

| accepted

Answered
Why do I get a graph that is symmetrical based on x=-2 when I draw a graph of y1=4*log((x+2))?
It is not clear what you wanted to plot. However, I think you misunderstand. It is still possible to evaluate the log of a nega...

4 dagar ago | 0

Answered
Tabulated Gauss-Kronrod weights and abscissae
I might presume the mp indicates some variation of the multi-precision toolbox. An old free version has been on the File Exchang...

4 dagar ago | 0

Answered
Solving symbolic trig equation
You can NEVER solve for those variables, at least as the equations are written. First of all, z never even appears. But since y...

4 dagar ago | 1

| accepted

Answered
How to get the value of an extra variable with fsolve
The simple trick is to use the output arguments from a function. Change your function header to look like this: function [F,r...

4 dagar ago | 0

| accepted

Answered
Find the intersection points between two data sets
Finding the intersection point is easy enough. [intx,inty] = intersections(data1(:,1),data1(:,2),data2(:,1),data2(:,2)) intx =...

5 dagar ago | 1

| accepted

Answered
numerical solution of a system of ODE which is not in standard form
Your question seems to be one of solving a system of ODEs with a mass matrix. For example in the help for ODE45, we see this opt...

6 dagar ago | 1

Answered
calculate tension by raphson newton in matlab
You have indicated these coefficients, although I worry there may be issues, because of the use of lower versus upper case W, et...

6 dagar ago | 0

Answered
Interpolating n-dimensional functions
First, IF you have a complete gridded lattice, then you don't want to use griddatan. That is DEFINITELY a BAD idea. Why? Because...

6 dagar ago | 1

Answered
What am I missing here?
Thank you. That makes it much easier for someone to offer you help. Now I'll be willing to look at the problem you had. It loo...

7 dagar ago | 1

Answered
How to extrapolate a contour plot?
Let me see. You have data in only 25% of the region of interest. Now you want to extrapolate that data into a region that compri...

7 dagar ago | 0

Answered
To solve non-linear equation by inversion notion
STOP. Is this nonlinear? Or is it linear? A*X = b is still LINEAR, even if the array is not square. Even in the linear case, t...

8 dagar ago | 0

Answered
how to use reshape ?
The good thing about reshape is IF you put in an empty argument, then it figures out how many columns you will need. But first,...

8 dagar ago | 2

Answered
Is an infinite for loop infinite?
We can always try it. Perhaps we can learn something about how the loop works, done by a careful test. Remember that doubles are...

8 dagar ago | 1

| accepted

Answered
how to fit 3 lines with one equation
Easy to answer. Is it possible? Of course. Anything is possible, though it may take a heck of a lot of work. I could even fin...

10 dagar ago | 0

Answered
Image Processing on point clouds
If you want to use image processing tools, you pretty much need an image. Those tools are not written to work without one, certa...

10 dagar ago | 0

Answered
Error in Eigen Values
Is KSr a double precision matrix, or a function, in the form of a function handle, or the name of an m-file function? That seems...

10 dagar ago | 0

Answered
Multiplication of two polynomials having different variables
The simple answer is to use the symbolic toolbox. If you have it, I cannnot think of a good reason why you would not use it. sy...

10 dagar ago | 0

| accepted

Answered
geometric progression and multiply by a common variable, help me pls.
So, you want this? B = 3; C = B*20*sqrt(2).^(0:10) C = Columns 1 through 9 60 84.853 120 ...

11 dagar ago | 1

Answered
f(x,y)<=0
I can see several ways off the top of my head. Consider some arbitrary implicit function. fun = @(x,y) x.^2 + y.^3 - 3; Easy ...

12 dagar ago | 0

Answered
how to decode the message 67 44 41 49 39 19 113 76 62 104 69 55.
A good clue to the answer "Is this code correct", when applied to a homework assignment like this is if you get something that m...

12 dagar ago | 0

Load more