Community Profile

photo

John D'Errico


Retired

Last seen: Today Active since 2006

DON'T contact me, as too many students then decide I am their personal consultant if I allow it. Anyway. I won't answer questions. PERIOD. I don't do your homework. I won't do consulting by mail. A retired mathematician, numerical analyst, woodworker, bridge player.

Statistics

All
  • Revival Level 4
  • Master
  • Quiz Master
  • Promoter
  • Top Downloads 2022
  • Top Downloads 2021
  • Top Downloads 2020
  • Top Downloads 2019
  • Personal Best Downloads Level 5
  • Editor's Pick
  • First Review
  • 5-Star Galaxy Level 5

View badges

Content Feed

Answered
Deconvolution results a single value
Convolution of two vectors yields a new vector that is longer than either of them. So if the vectors have length N and M, then t...

11 hours ago | 0

Answered
Files added to path won't run unless I rename them first.
Never use the directory structure that comes with MATLAB to store your own files. Why not? MATLAB caches those directories at s...

15 hours ago | 1

| accepted

Answered
manipulation of yearly, quarterly, monthly, weekly and daily dates using datenum
I don't see the problem. It mainly looks like you need to understand the concept of leap years. That would be crucially importan...

22 hours ago | 0

Answered
Cubic Spline not printing
It has been a month since you asked the question, so I'll post an answer. Note that your data has x=[1 2 6 3 5 6 7 8 9 7 6 5 ...

1 day ago | 0

Answered
Does the built in function singular value decomposition (svd) do the correlation matrix for you?
The SVD does NOT perform the re-scaling involved in a correlation matrix. It just uses the array you give it, with no preemptive...

2 days ago | 0

| accepted

Answered
finding fold curve in 3D surface
You have a surface, generated using meshgrid. I would split that surface into a triangulated mesh. So two triangles per rect in ...

2 days ago | 0

| accepted

Answered
Difference fit result form nlinfit and lsqcurvefit
And, so? Many problems will have multiple locally optimal solutions. Neither of those tools even hopes to be a globally optimal...

2 days ago | 0

| accepted

Answered
Define a family of functions
DON'T DO IT THAT WAY. Instead, define ONE function. One function to rule them all. (Sorry. That last part just slipped out.) Se...

2 days ago | 1

| accepted

Answered
Draw the sphere to find the radius of the sphere
Estimation of the sphere parameters is not too difficult. First, since you have shown no data, I'll make some up. XYZ = randn(5...

3 days ago | 0

| accepted

Answered
How can I generate a trigonometric formula for the following case?
Theta= [39.8414239035357 38.0423831220740 35.9925962696569 33.6629179282453 31.0086860615562 27.9576609766453 24.3833553424339...

3 days ago | 2

Answered
Randomize vector avoiding consecutive values
Typically, rejection would be necessary. Of course, if your initial vector were composed only of two elements, then there are on...

4 days ago | 0

Answered
What does this plot mean? Can an equation be made of it?
Can you get an "equation" for it? No. At least not any more than what you already have. Anyway, an equation involves an equality...

4 days ago | 0

Answered
is that really necessary to measure and put the weakness of the thesis if it is not scope of the work?
This is totally inappropriate to Answers, since it has nothing to do with MATLAB. Even if MATLAB would be involved with your the...

4 days ago | 0

Answered
Data fitting using thin-plate spline/interpolation
This is a common problem people have with splines in any form. They hope to see some nice simple function they can write down. M...

5 days ago | 2

Answered
How to display a message as flashing and in my desired color and font size?
You can do that, but since disp is not written to accept those extra arguments, it might not work. Wanting code to do what you w...

5 days ago | 1

Answered
3d plot of Tridimensional parabolic motion
It should look strange. Why? g=9.8; z0= 14325; x0=0; y0=0; V_0= 200*0.3048; gamma=0.78; V_0x=V_0*cos(gamma); V_0y=V_0*co...

6 days ago | 0

| accepted

Answered
Can I define or change the direction of 'reshape'?
No. You cannot do so. You cannnot change how reshape works. HOWEVER. Nothing stops you from changing that afterwards. For examp...

6 days ago | 1

| accepted

Answered
Isolate horizonal part of curve
What part of this curve is horizontal? syms x F = exp(-10*x) fplot(F,[0,3]) Well, clearly, ithe horizontal part lies above x...

6 days ago | 1

Answered
A way to write "if x is in y matrix do this"
You CANNOT use ismember to test if a number is in an interval. Even ismembertol does not do that. Using code to do something it ...

7 days ago | 0

Answered
numerical integration inf to inf
You cannot use trapezoidal rule to do the integration exactly fully to the endpoints, since the shape of that function is too ex...

7 days ago | 0

Answered
What is the maximum size of *.mat file?
There is no maximum size of either file. It would be strictly dependent on the memory you have available. Well, you could say ...

7 days ago | 0

Answered
Upper bound curve that passes through the extreme (highest) points
I would argue a convex hull is probably at least close to what is wanted. That it works here because the envelope is roughly a c...

8 days ago | 1

Answered
How to find number of bit change between binary numbers?
Read what @Jan said. xor followed by sum is the simple way to go, of course. And we really have not been given enough informatio...

8 days ago | 1

Answered
infinity recursion with in the program
What do you expect? Look carefully at your code. I've extracted the only lines that matter below. function stabil = punktStabil...

8 days ago | 0

| accepted

Answered
Most efficient way to solve a symbolic equation system with more than 2k unknowns
Symbolic solvers are SLOW. Well, comparatively so. This is partly because they use high precision. The computations, if they are...

9 days ago | 0

Answered
I want to ask how to define the partial fraction code single number located at the numerator?
Remember that MATLAB does not understand implicit multiplication. That is, 4x is not interpreted as 4*x. In MATLAB, 4x is just a...

9 days ago | 0

Answered
How to extrapolate the data while some data is already supplied on one spine?
Extrapolation using a spline (in any form)? A terribly bad idea in general. Extrapolation over a long distance? Another terribl...

9 days ago | 0

| accepted

Answered
Why DerivativeCheck would be allowed to be on while there is no GradObj?
You can set other options that will be ignored if they are not applicable. Would you rather have the code fail for no reason on ...

10 days ago | 0

Answered
Finding the first index of a row where all integers of a defined list have occurred
Given a vector, can you simply find the first index where all have occurred? Just use ismember. x=randi([1,4],1,100) [~,locs] ...

10 days ago | 0

| accepted

Answered
How do I separate terms using symbolic expression?
Trying to get a symbolic tool to give you exactly the form you want to see is often terribly difficult, and usually not worth th...

10 days ago | 0

Load more