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Apr
23
comment Most efficient way to compute eigenvectors / values of this matrix?
There is a disadvantage to Cardano's method for solving the general cubic polynomial, that even when all three roots are real, the intermediate expressions for the roots may involve complex arithmetic. When it known (as here) that all three roots are real, there is an alternative approach using trigonometric functions instead of radicals to give only real expressions for the three roots.
Apr
23
comment Most efficient way to compute eigenvectors / values of this matrix?
Note that if $A$ is a real symmetric matrix, its eigenvalues are real no matter what the physical motivation.
Apr
19
revised About training HMM by using EM
corrected spelling in title
Apr
16
comment Need help writing the code for the following optimization
That is: $$\min_{\text{real } Z} ||Y-Z||_2 + ||F(Z)||_1$$ should be the objective function. Even this you might prefer to restate in terms of $W = Z-Y$, using $||W||_2 + ||F(W+Y)||_1$, where $W$ ranges over real arrays the same size as $Y$.
Apr
16
comment Need help writing the code for the following optimization
The short answer is to rewrite the objective function with real array $Z $ instead of ifft(X) and $F(Z)$, the fast Fourier transform of $Z$ instead of $X$.
Apr
15
reviewed Approve FFT (Numerical Recipes in FORTRAN 77)
Apr
15
reviewed Reviewed Need help writing the code for the following optimization
Apr
15
comment Need help writing the code for the following optimization
Please explain more about the restrictions on the entries for $X$ over which the minimization is to be performed. For example, must $X$ be real values?
Apr
15
revised Need help writing the code for the following optimization
replaced image of expression with MathJax formatting, added links to Matlab doc
Apr
15
reviewed Close semidefinite programing in cvx
Apr
15
reviewed Leave Open Branch avoidance for performance with modern compilers?
Apr
15
reviewed Reviewed Efficiently rotate vector in 2D (and 3D)
Apr
15
comment Efficiently rotate vector in 2D (and 3D)
Are the vectors to be "randomly" rotated based at the origin? If you want to achieve a specific distribution, say a uniform distribution, then it would be helpful to Readers to see your implementation using "the division and the square root" before they try to offer an equivalent that avoids these.
Apr
15
reviewed Reviewed How can I simulate a PCM (erythritol) charge and discharge with Matlab?
Apr
15
comment How can I simulate a PCM (erythritol) charge and discharge with Matlab?
The Question is too brief for many Readers to recognize what you want "a Matlab code" to do. Using so few words does not promote a quick response from your Readers. Also you might look at how to post mathematical expressions here using $\LaTeX$.
Apr
15
reviewed Reviewed IVP Using Numerical Methods
Apr
15
comment IVP Using Numerical Methods
Two points. First, at least part of your problem about showing $e(t)$ satisfies the IVP is trivial. You should at least spot which of the two parts is easier. Second, the last part of the Question assumes $f(t,y) = \lambda y$. This lack of dependence of $f$ on "time" $t$ is often referred to as an autonomous system. Special deductions can be made from this property.
Apr
12
comment Pure math questions arising in computer vision, and the need for mathematicians to solve them
Work out how to email me and I'll gladly give you some free advice.
Apr
11
reviewed No Action Needed What are alternatives to openbabel to convert CML file to image?
Apr
11
comment Pure math questions arising in computer vision, and the need for mathematicians to solve them
As anecdotal information, I was approached last week by an out-of-state recruiter for a firm that seems to use some computer vision technology to produce dental appliances. I never spoke to anyone but the low-level recruiter, but the job requirements write-up he shared mentioned algorithms and data structures and computational geometry. He said that they were having trouble filling the position due to programmers often not having enough experience or interest in the mathematical aspects.