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John D'Errico


Retired

Last seen: Today 2006 以来アクティブ

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.

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How to create random matrix with specified step in interval [a, b]
You can also use indexing. The idea is to generate random indexes. ValidRandomSet = 5:3:34 m = 7; n = 6; ind = randi(numel(V...

約2時間 前 | 0

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Interpolate using a different method without the original image
Um, no, or, yes. Anyway, you cannot do it directly. And it may be completely impossible to do. All of that depends on several th...

2日 前 | 0

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How to find the volume of cross-sectional area of a cylinder
Is there a ready made function that will do the mathematics for you, based only on an inequality? No. You will need to do some m...

2日 前 | 0

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回答済み
Error solving bvp4c - Singular jacobian
You have a simple classical ODE, with two INITIAL conditions, not boundary conditions at different ends. So use a tool like ODE4...

5日 前 | 0

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noisy plot after calculating first derivative
You should recognize that differentiation is a noise amplification operator. So any small amounts of noise in your signal, even ...

5日 前 | 0

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fminsearch with side conditions
Generally, the solution is to not use fminsearch. Use a better optimizer instead. It will be faster, and you will get a better a...

5日 前 | 0

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Obtaining value of highest order derivative over simulation period
Can you use schemes like ODE45, combined with gradient to compute exact estimates of the high order derivatives? Sadly, no. High...

6日 前 | 1

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Acceleration at the center of the triangle
If you have some known parameter at the three corners of a triangle, then the best estimator of that parameter at the center of ...

6日 前 | 1

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How to use bitn
You cannot define a scalar variable as a binary one with an arbitrary number of bits. You can define integer variables, with a s...

8日 前 | 0

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Why I'm getting error (too many arguments) in my integral
You need to pay MUCH more attention to your code. For example, just a quick look shows this: Intdoble6=int(int(2*y^2,x,0,1)4*x...

8日 前 | 0

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I nee to write a code to solve a definite integral. The output format has to be fprintf.
Do you understand that MATLAB REQUIRES a multiplication operator? You cannot just put a number next to a letter, and expect MATL...

9日 前 | 1

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Maximum Likelihood Estimation function
Is there another way? Why not negate the function, and then use a tool like fminbnd? Or fminsearch. Or fmincon or fminunc, or .....

10日 前 | 0

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What optimizer should I use?
This is not a problem of finding an optimizer. This is a problem of understanding how to formulate a problem so that it is possi...

11日 前 | 0

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simulation stopped because of step size tolerance and constraints
Let me see. You posed an optimization problem. The solver returned a result, one that SATISFIES the tolerances you posed. You we...

11日 前 | 0

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Revolving a curve about the y-axis to generate a 3D surface
Certainly. Just write the code yourself. Seriously, it is not difficult. Consider the function y = f(x). f = @(x) x.*(1-x); ...

11日 前 | 0

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matlab rank of a matrix
Because the call: R = ones(100,100); rank(R,1e-20) attempts to do something that is demonstrably silly, in terms of double pr...

11日 前 | 0

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which project of these projects will be easy with matlab?
I think you do not understand. ANY project can be either easy, or too difficult for you to handle. What matters is if you unders...

16日 前 | 0

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How should I approach solving differential equation as function of two variables r, k?
While you COULD use an ODE solver, this is something you would ONLY do if the ODE had no analytical solution. And this ODE has a...

16日 前 | 1

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Fmincon too many input arguments
How are you using it? That is, how did you call the function try_no_gradient(u0)? When you get an error message, show the COMPL...

17日 前 | 0

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How to subtract only certain elements of a vector
a and b are not vectors in your question, they are arrays. However, if you want to do this, nothing stops you from selecting th...

17日 前 | 0

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Plot the graph using non linear equation
A nonlinear problem like this is called an implicit function. You can think of the value of h, as a function of theta, but there...

18日 前 | 1

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convert current date and time to char
Easier than you think. First, what is the current time? format long g CurrentTime = now That might not seem terribly helpfu...

18日 前 | 1

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Limit angle in [-90,90] degree
You cannot simply constrain an ODE solver to stay within bounds. However, almost certainly, if the ODE solver wants to go outsid...

20日 前 | 0

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Code involving factorials and a given value
Now that you have a looped solution, let me show how to solve the problem more directly. There are actually several solutions I ...

21日 前 | 1

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how to solve this differential equation system symbolically?
This seems like a homework problem. But Walter has already given an answer, that I think is not helpful, since dsolve will fail ...

21日 前 | 0

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Optimization to find a deterministic number
Huh? This question is pretty confusing. But let me see where it goes. First, it seems you claim that g(x) is the solution of an...

22日 前 | 0

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How to rotate about an axis parallel to x axis?
Simple. Effectively, you transform the problem to a rotation around the x axis, then after the rotation, you tranform back. For...

24日 前 | 1

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Matrix from measured data is singular, what could be the reason?
In no place in this thread have I seen the matrix A. I've seen various versions of it however, with various numbers of rows. I'v...

24日 前 | 0

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Reinforcement Learning toolbox missing functions
If you have a current version of that toolbox, it should have those tools. which rlDiscreteCategoricalActor which rlValueFunct...

25日 前 | 0

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Calculate the distance between points in a large data set
LEARN TO USE MATLAB. Do not create numbered and named variables. DO create vectors and arrays. Use them. Since all you have pos...

27日 前 | 1

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