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Vladimir Sovkov


St. Petersburg State University

Last seen: 11 days ago |  Active since 2014

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Professional Interests: computational physics, applied mathematics

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Wigner 3j-6j-9j
Wigner 3j-, 6j-, 9j-symbols

8 months ago | 8 downloads |

Answered
How do I uninstall MathWorks Products on Windows when the uninstaller fails?
I have a similar but somewhat different problem. For a couple of years, I used Matlab 2019b with Windows 10. This year I decided...

3 years ago | 2

Answered
How to fit to an infinite series function?
An iterative solution instead of the symbolic one can be more productive this case, like this one x=[0 5 10 15 20 30 45 60 75 9...

4 years ago | 0

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Answered
How to average columns of matrix without loop?
reshape(mean(reshape(A',n,[]))',size(A,2)/n,[])'

4 years ago | 0

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Answered
When i try this sym('x')^y i get an error message
You cannot compute this directly because the integers are larger than matlab is able to treat. You can try b = sym(log10(18008...

4 years ago | 1

Answered
How to plot step functions in Matlab
syms x; y=piecewise(x<0,0, 0<=x<2*pi,exp(-x).*cos(x), x>=2*pi,2*exp(-x).*cos(x)); t=linspace(-pi,4*pi,1000); plot(t,subs(y,x,...

4 years ago | 0

Answered
Adding or subtracting the same number
n=4; % array length x=zeros(1,n); % sample array d=0.4; % value to be added/subtracted k=rand(1,n); % uniformly random number...

4 years ago | 1

Answered
How to plot complicated exponential function 4.82 (1 + 0.35 e^ −4.07t ) / (1 − 0.35 e^−4.07t) on matlab
Use the element-wise division when computing y: y = ((4.8184) * (1 + 0.3497.*exp(-4.0719.*x))) ./ (1 - 0.3497.*exp(-4.0719.*x))...

4 years ago | 1

Answered
make different numbers with the same digits
x=1342; y=str2num(sort(num2str(x),'ascend')); % smaller z=str2num(sort(num2str(x),'descend')); % bigger

4 years ago | 0

Answered
is it possible to write a code that examine and analyze that a data in vector having 100 values, so recognize that if one or two very high as compare to other data?
This is known as the problem of locating outliers. Various approaches were proposed. E.g., the one based on the median absolute ...

4 years ago | 0

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Answered
flip the sign at zero crossing point
Data1 = [1,0,1,1,0,1,1,0,0,1,0,1,0]; k=find(~Data1); if ~isempty(k) if k(end)<numel(Data1) k(end+1)=numel(Data1)...

4 years ago | 0

Answered
Issue with 'for' loop - trying to iterate through and change certain values to 0 in array
If the equality must be exact, just x_results(x_results==.3095)=0; and nothing else (sometimes can produce an incorrect result...

4 years ago | 0

Answered
How can I create a script that calculates this combinatorial?
C=nchoosek(n,r)

4 years ago | 0

Answered
Specify eigenvector for eigs
Matlab documentation: 'StartVector' — Initial starting vector random vector (default) | vector Initial starting vector, spe...

4 years ago | 0

Answered
How to "wrap text" on pushbutton string?
Use the cell array with entries containing text fragments to be shown in separate strings.

4 years ago | 0

Answered
how to implement the algorithm for approximating Cosine using the Taylor series
syms theta n=4; taylor(cos(theta),'Order',n)

4 years ago | 0

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Submitted


aux2bib
BibTex (LaTeX) sublibrary from an AUX file

4 years ago | 1 download |

Answered
Is there any way to accelerate the solving of a series of large sparse positive definite linear equations "Ax=b" with same "A" and different "b"?
It depends... Besides inv(A), you can try A\eye(n), pinv(A)--all of them are equivalent for a well-conditioned A and different ...

4 years ago | 0

Answered
Is there any method to calculate the inverse of matrix which changed a few values?
I am not sure how much profitable it is numerically, but the Sherman Morrison theorem can be a way, see https://en.wikipedia.org...

4 years ago | 1

Answered
What does ''all'' mean in M = min(A, []. ''all'') ?
All this is fairly well described in the matlab documentation. min(min(A)) and min(A, [], ''all'') are equivalent for 1D and 2D ...

4 years ago | 0

Answered
If I have multiple function, then how can I get the function of min(fun1,fun2,fun3,...)?
xmin=min([R1(x(:)');R2(x(:)');...]); % to get a correct result, the argument must be a row-vector: x(:)' turns any input array t...

4 years ago | 0

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Answered
Is there a bug in the if function
This is not a bug in the if function but an artefact of the rounding of the matlab bit-wise arithmetics. To avoid this effect, s...

4 years ago | 0

Answered
Angle between two lines in frontal plane
If, as it looks in the figure, (...Y) are the verticle coordinates and (...Z) are the horizontal coordinates, then the basic geo...

4 years ago | 1

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Answered
solve function give a wrong solution
syms x solv = double(solve( (1+x/12)^12 == 1.02)) There are many solutions. The one you are interested in is rather 0.01981897...

4 years ago | 0

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Answered
How to see the current value of the variable in "fminsearch" optimization?
optimset('Display','iter'); From Matlab documentation: 'Display' — Level of display 'notify' (default) | 'final' | 'off' | 'n...

4 years ago | 0

Answered
showing the distance between the two plots on two curves at regular intervals on the same plot
t=0:0.2:10; % avoid loops wherenever possible, use element-wise operations instead x=t.^2; y=0.5*x+10; % the same as "y=0.5*t...

4 years ago | 0

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Answered
Writing into .txt file
T = [v angle_random]; % this is if you want a 2-column file save('random_cylind.txt','T','-ascii','-double'); % explore availab...

4 years ago | 0

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Answered
Debugging using external editor
https://www.mathworks.com/help/matlab/matlab_external/debugging-on-microsoft-windows-platforms.html

4 years ago | 0

Submitted


aux2bib
BibTex sublibrary from a LaTeX AUX file

4 years ago | 0 downloads |

Answered
How do I record the location of a specific value in a set of data?
a=[0 0 0 0 1 0 1 0 0]; k=find(a==1,1)

4 years ago | 0

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