John D'Errico

Retired

Last seen: Today | 2006 年からアクティブ

Followers: 21 Following: 0

メッセージ

A retired applied mathematician, consultant, sometime mechanical engineer, numerical analyst, woodworker, bridge player. Please DON'T contact me, as too many students then decide I am their personal consultant if I allow it. I won't do consulting by mail.

統計

All

バッジを表示

Feeds

回答済み
Are there MATLAB functions or scripts to perform boolean operations on triangulated solids?
Are there such codes in MATLAB? Yes. I wrote them. intersect, union. In 2-d and in 3-d. (Not sure if I wrote a setdiff variant. ...

約4時間前 | 0

回答済み
Product of matrices over finite fields
Even in the simple case of F_2 matrices, I'm not sure it is easy to do better than brute force. But no, you don't need to write ...

1日前 | 1

| 採用済み

回答済み
Multi-Parameter function minimization with many many parameters
Let me try to help, a little at least. Why is fminsearch so bad at high dimensions? It is just not designed for that class of ...

3日前 | 0

回答済み
Solve nlp equation system with variables spanning more than 40 powers of 10
Are the variables potentially going to vary by that many powers of 10? If so, then you would have the solver work in a log space...

7日前 | 0

回答済み
Solve 𝑔 ′ ( 𝑥 ) = 0 for z in terms of N, a positive integer
First, it is not a cubic equation! Yes, you can replace sqrt(x) with a new variable z, thus a transformation. But doing so can ...

7日前 | 0

| 採用済み

回答済み
With k（0<k<0.5） and u（-1<u<1) as independent variables and x and y as dependent variables, how do you graph x and y, respectively, for a system of implicit function equations?
You have 2 parameters, k and u. If you were to fix those parameters, then you could solve for the solutions. There would be zero...

8日前 | 0

回答済み
4 nonlinear equations by using Newton's method
Why are you writing Newton's method code to solve a problem? Never write code to do numerical methods work, if far better code i...

10日前 | 0

回答済み
Is there a function in matlab to find temperature, density ecc.. values outside the standard atmposphere?
Um, not really, and certainly not easily or in any good way. Something like temperature can vary HUGELY outside the atmosphere,...

11日前 | 0

回答済み
Issue regarding the result from symbolic computation
If you have this: a11 = 1/2; a12 = 1/2; a22 = 1/2; A = [a11 a12 0; a12 a22 0; 0 0 0] The eigenvectors were found as: [V,D] =...

12日前 | 1

回答済み
Calculating Perpendicular Distance Between Detected Edge and Smoothing Function
If your curve is represented as a sequence of points (which is always possible) then you can use my distance2curve utility. It f...

12日前 | 1

| 採用済み

回答済み
How to draw the function relationship graph between two or three variables, where these variables are solved by a system of equations.
Not everything you might want to do has an answer. You ask to "draw" the relationship between variables. (For a fairly vaguely s...

13日前 | 0

回答済み
How to create a smooth curve through data points?
Just coming back to this, as I did not see the data provided. (Sorry to @Gerard Feeney) But this is a difficult thing for multi...

13日前 | 1

回答済み
Is it possible to select the parameters in the approximation equation using MATLAB?
Yes. Use the curve fitting toolbox. help fittype help fit Note that the estimates of these coefficients will be very uncertai...

14日前 | 0

回答済み
HI, while doing a small calculation part, from my class note, in matlab, im getting the result as inf, can i know how to convert the inf value into realnumbers.
Of course D0 is undefined. You created the variable Do. There is a difference between the number 0 and the letter o. That Do is...

16日前 | 0

回答済み
Need help with curve fitting
Um. NO. Yes, there is a language problem, and what you write is confusing. But you are not doing what you claim to want to do. W...

18日前 | 1

回答済み
solving a nonlinear equation with complex numbers
syms R positive % positive implicitly implies real also syms X real syms Zo Z=(R*1i*X/(R+1i*X)); r=(Z-Zo)/(Z+Zo) r = simpli...

19日前 | 0

回答済み
Warning: Equation is badly conditioned. Remove repeated data points or try centering and scaling.
Do NOT use polynomials to model data like this In fact, do not use high order polynomials, pretty much ever. FR = load('FR.txt'...

22日前 | 2

回答済み
Recursively reversing large vector efficiently
An old question with an already good answer. Regardless, it explicitly asks about recursive schemes to flip a vector. And I can ...

23日前 | 0

回答済み
Fixing biased random number generation
What is the goal of this? That is a good question, as asked by @埃博拉酱. You should recognize that the result of this operation w...

24日前 | 0

回答済み
My end value "tc2" comes out as "NaN + NaNi", in the following script and I cant figure out why.
A NaN means you are doing some operation that has no meaningful result. For example, what is 0/0? 0/0 A mathematician will tel...

25日前 | 0

回答済み
Sparse matrix memory understanding
I think you missed a zero. By the way, 5% sparse is NOT at all what I would consider sparse, or for there to often be a gain. L...

27日前 | 0

回答済み
Fittype and fit do not work as expected (in a curve fitting)
x = [1 4 9 15 25 35 45 55 65 75 85 95 150 250 350 450 900]; y = [0 335 28 37 9 4 3.5 2 1 0.7 0.6 0.5 0.3 0.1 0.01 0.005 0.001];...

28日前 | 2

| 採用済み

回答済み
Newton Rapson method code question
Actually, this is surprisingly nice looking code. (A true compliment from me, given most of the student codes we see on here!) Y...

約1ヶ月前 | 1

| 採用済み

回答済み
Converting an STL file to a 3D Surface/Equation
Um, I think you misunderstand a few things. It seems the STL model actually has thickness. So you have exported the entire thi...

約1ヶ月前 | 0

回答済み
I want the genetic algorithm to begin with intial parameter and this is not happened can you help me for making the genetic algorithm begin with the intial parameter?
I think you don't understand GA. It does not use a start point. It starts with an initial population of points from the sample s...

約1ヶ月前 | 0

回答済み
How do I convert a symbolic expression to a string?
Simple enough. Note the changes I made to your last line only. I could also have done it using character vectors, but then I wou...

約1ヶ月前 | 1

| 採用済み

回答済み
Plotting a volume in 3D
Your question is somewhat incomplete, as to what you mean by plotting a solid volume. I'll assume you may mean something like th...

約1ヶ月前 | 0

回答済み
How to numerically calculate volume under the curve?
You have a surface. (Not a curve as I might say.) How do you compute the area under that surface? Simple. Just call trapz twice....

約1ヶ月前 | 1

| 採用済み

回答済み
ode45 integration issues for some choices of physical parameters,
This is an absolutely classic case for a stiff system, where for some sets of system parmeters, you have two or more things happ...

約1ヶ月前 | 0

回答済み
How to choose 60 unique coordinates ('A') from 600 coordinates('B'), nearest to 60 other coordinates('C')
As I pointed out to @Voss and @Star Strider, if the points in B mst be unique, then there is an issue. If you simply choose the ...

約1ヶ月前 | 1

さらに読み込む

John D'Errico

Retired

統計

MATLAB Answers

MATLAB Answers

Cody

Cody

File Exchange

File Exchange

File Exchange

File Exchange

MATLAB Answers

File Exchange

File Exchange

File Exchange

Feeds