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John D'Errico


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5,234 2006 年以降の合計貢献数

(Don't contact me. I won't answer questions.) A retired mathematician, numerical animalist, woodworker, bridge player.

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How to determine eigenvalues of symbolic matrix?
What form would you expect? Is there a reason why you expect the eigenvalues of a 4x4 symbolic matrix to be some nice pretty thi...

約16時間 前 | 0

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fminunc gets first-order optimality of zero on iteration 0, does not find optimum
First, this appears to be a ONE parameter optimization. Do not use fminunc for that. Instead, us fminbnd. It will be more robust...

約23時間 前 | 0

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symbolic toolbox problem ?
A strong possibility is you have overwritten/overloaded the stored value of pi. >> clear pi >> pi ans = 3.1415926...

1日 前 | 0

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Find whether there is a trend over time or the data is completely random
This really is not a MATLAB question, as you have no idea how to compute what you want, and your question is too vague to have a...

2日 前 | 0

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Weighted Least Square Fit regarding equal parts of the xaxis
You can't directly supply weights as an option to laqcurvefit. Better is to use lsqnonlin for this, since you return the residu...

2日 前 | 0

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Given that A is a sparse matrix, norm(A(i,:)) takes a very long time. Why and can one do better ?
You really don't want to use loops to do something like this. >> A = sprand(10000,10000,0.001); >> timeit(@() norm(A(1,:)))...

3日 前 | 0

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C = union( A,B ) is too slow. Is there any faster way given that A and B are ordered.
You could use unique. It would produce the same result, except that it will not be faster. A = sort(randi(1e7,1,1e6)); B = sor...

3日 前 | 0

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Kindly help me to obtain the first four numerical solution of given trancedental equation "luck 1"
Have you not tried plotting it? It is so easy to say that you want the "first" 4 roots. >> vpa(subs(luck1,x,eps)) ans = -1.7...

3日 前 | 0

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How to generate random numbers with constraints and different boundaries (for a high dimension)?
Neither of the choices on the FEX are directly a solution. randfixedsum fails because it explicitly assumes uniform bounds on th...

4日 前 | 0

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finding roots of equation in matlab
In general the roots of a 6th degree polynomial with unknown coefficients cannot be found in an algebraic form. At least not unl...

5日 前 | 1

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Estimating parameter uncertainty with fminsearch
I think I am starting to understand what you are askng. One very good option is to use abs. I've been told I could use better ab...

5日 前 | 0

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How can i randomly insert 14 1's in a array of two thousand zeros?
A = zeros(1,2000); A(randperm(2000,14)) = 1;

5日 前 | 2

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How to solve this ode problem
Use none of them. This is NOT an ODE problem, except that you seemed to want to write it as such. It is certainly not something ...

6日 前 | 0

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Calculate the distance between a linear regression line and the data points
I am confident that what you are asking is an orthogonal distance, not the vertical difference, frequently known as the residual...

6日 前 | 0

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How do I get the intersection function of 2 surfaces?
The intersection function will rarely exist as a "function". At best, it is an implicit function, thus a problem with solution l...

8日 前 | 0

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ode,dsolve,spline,ode interp, differantial
You are not asking to do anything more than to integrate a spline, and perhaps to plot the result as a function of x. (You don't...

8日 前 | 0

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Integrating from polyint(p)
Sorry, but polyint cannot integrate a rational polynomial, and certainly not over an infinite region. Depending on the roots of ...

9日 前 | 0

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How to optimize matrix multiplication speed?
Do this: P = PHI*(P + Q)*PHI' + Q; While it may look exactly like the line of code you wrote, in fact, it is the same. Matrix ...

9日 前 | 0

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Algorithm to extract linearly dependent columns in a matrix
It is difficult to answer this. Consider a simple matrix: format short g A = rand(4,5) A = 0.73796 0.36725 0....

9日 前 | 0

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How can I create a function with random imputs? I have to create a function called tri_area that returns the area of a triangle with abse b and heigh h, where b and h are input arguments of the function in that order
I think you may be confused. I believe what is asked is for a function with ARBITRARY inputs, in the sense it can be called with...

9日 前 | 2

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The accuracy on my LSTM deep learning neural network will not exceed 62.96%
You have shown no data, so we cannot truly say if you are doing something wrong. However, it sounds as it what you are doing is:...

9日 前 | 0

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how can i get a number as an answer?
You got a number. :) I know, its net a very useful looking number. As s floating point sym, use vpa. vpa((23401992239682647381...

9日 前 | 0

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why does similar code generate complex numbers?
What, for example, are the THREE cube roots of a negative number? We can find them all as solutions to the equation syms x xs...

11日 前 | 0

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Is there a tool for drawing diagrams that connect equations?
I don't think there is a tool in MATLAB that will take a set of equations in arbitrary order, and then create this diagram. Yo...

11日 前 | 0

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How can ı solve this constraint optimization problem?
Many things you can do, but since this is your homework, and there are already answrs posted, I'll just suggest a couple of thin...

11日 前 | 0

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USING MEX TO SPEED UP THE CODE
As a counterpoint, there are some issues to consider. Much of MATLAB is already compiled code, at least in the hard working part...

11日 前 | 1

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help solving differential equations
I think you have multiple problems here, now that you claim to have the correct equation. DSOLVE finds an analytical solution to...

11日 前 | 0

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Simplifying a algebraic or numeric expression to lowest possible power
The problem is, there are multiple solutions, because sqrt is not as simple a thing as you like. syms x >> y = sqrt(x.^2) y ...

11日 前 | 0

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Install 2 instances of Matlab on the same PC
Yes, and no. I frequently have several old versions of MATLAB on my computer. Walter has many as I recall. The only issue is if ...

11日 前 | 0

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Is there any method to calculate the inverse of matrix which changed a few values?
Bruno is correct in how to solve the problem, and also SOME of the issues with it. If you use this tool multiple times, the floa...

11日 前 | 0

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