John D'Errico

Retired

Last seen: Today|2006 이후 활성

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 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...

1일 전 | 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...

2일 전 | 0

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强化学习工具箱缺失的功能
If you have a current version of that toolbox, it should have those tools. which rlDiscreteCategoricalActor which rlValueFunct...

3일 전 | 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...

4일 전 | 1

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Optimization terminated: average change in the fitness value less than options.FunctionTolerance.
Star has answered your uestion. However, I want to expand on what was said there. Too often, I see people confused by this messa...

5일 전 | 0

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Describe non-convex region with linear inequality constraints
Nothing stops you from dissecting a polygonal region into triangles, even if not convex. As Matt said, you CANNOT use a set of l...

5일 전 | 0

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How to find area of enclosed region (i.e., calculate Green's Theorem) in MATLAB?
You have a sequence of points in a loop. Create a potyshape from them, then compute the area. help polyshape methods polyshape...

5일 전 | 0

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How to find matrix S, given by this equation
There is no unique solution. Or, there may be no solution at all. This looks vaguely like an algebraic Riccati equation. Your p...

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从平稳分布随机数
Simpler to accomplish than others have said. But first, do NOT define those probabilities as separate variables!!!!!!!!!!!!!!!!!...

7일 전 | 0

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Vpa conversion of whole file
I'm sorry. You cannot now convert those files automatically, to take lines like a = 5; And automatically have MATLAB see thos...

8일 전 | 0

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Fitting line to a curve
Easy. Use findpeaks, to locate the sequence of points that represent the successive maxima of the curve. Use an interpolatin...

8일 전 | 0

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Symbolic toolbox substitution causing large values
A REALLY bad idea is to name your variables things like var, as that is also the name of a terribly useful function. So your n...

9일 전 | 0

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How can a curved surface be generated with a thickness and density?
Sorry, but this is the kind of thing that is virtually impossible to do in any intelligent way. You are asking for some strange ...

10일 전 | 0

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dsolve isn't solving my symbolic ODE correctly
Look carefully at your solution, because you missed something. gamma_s_sol(t) = -7.7215e-11*exp(-8.6936*t)*(5.7469e+08*exp(8....

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How to fit a curve into contour plot?
Sometimes it is easier to just draw the curve yourself. I say this because the curve you drew might not have been the curve I wo...

11일 전 | 0

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curve fitting tool custom equation
A general problem with the curve fitting toolbox is that it does not understand the mathematics of a model you pose to it. Not t...

12일 전 | 1

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how to determine the arithematic operations in a code?
Sorry, but not easily. Flop counts were removed from MATLAB over 20 years ago. //www.tianjin-qmedu.com/matlabcentral/answers/...

13일 전 | 1

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How do I I get the first 15 solution of the equation
First, make the problem simpler. You have TWO constants. Change the problem to have only one constant. That is, essentially tran...

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Converting Matrix of binary in to decimal
What does this do? mat*2.^(4:-1:0)'

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How to solve the following homogenous equation?
A =1.0e+08 *[ -3.1265 -1.0000 0 -1.0000 -4.5841 -1.0000 0 -1.0000 -0.2345]; First, let me verify ...

15일 전 | 1

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Replace values with zero and zero with values in matrix simultaneously
Easy. SwRailNodeDemand = [1 0 4 -5 0 6 8 -11 7 9 10 0; 2 1 0 0 0 0 0 0 0 2 0 -3; 3 3 4 1 1 0 0 0 0 0 0 -1; ...

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How can I determine the value experimental data settled on?
I don't see the problem. Throw away most of your data. (At least to determine the long term behavior.) Then compute the mean. O...

16일 전 | 1

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fsolve completed because the vector of function values is near zero as measured by the value of the function tolerance,
I think you do not understand these things: A system of NONLINEAR equations can have multiple solutions. That a numerical solv...

17일 전 | 2

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Changing numerical precision for math operations
You have TWO choices for floating point precision, double or single. A = double(1); B = single(2); C = A + B class(C) Arith...

18일 전 | 1

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Random triplets not asymmetrically distributed
If you wish to sample from the set of triplets that sum to exactly 1, where each elemnt is discrete, then you do NOT want to use...

18일 전 | 3

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Find minimum enclosing circle
So let me use my own code to solve your problem. im = imread('IMG_3108.jpg'); [redpixr,redpixc] = find((im(:,:,1) > 140) & (...

18일 전 | 0

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Smoothing just part of the data
Um, No. Why should there be? In fact, extracting the part you want to smooth, and then overwriting that smoothed fragment back ...

19일 전 | 0

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Matrix dimensions must agree when doing an elementwise operation
How many elements are there in the vector a? (101) How many elements are there in the vector b? (101) How many elements are th...

19일 전 | 1

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what is the time complexity of function 'reshape'
Essentially, almost zero time (a small constant amount that is almost negligable.) All reshape itself does is modify a flag atta...

20일 전 | 1

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Error in solving using Ode45 initial condition are y(1) = 0, y(2) =0 and y(3) =0.
Sorry, but not easily. ODE45 is an INITIAL value solver. This is a variation of boundary value problem, where you have values at...

20일 전 | 1

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