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Vladimir Sovkov


St. Petersburg State University

Last seen: 4 dagen ago Active since 2014

Professional Interests: computational physics, applied mathematics

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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...

ongeveer een jaar ago | 1

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...

bijna 2 jaar ago | 0

| accepted

Submitted


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

bijna 2 jaar ago | 9 downloads |

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

bijna 2 jaar ago | 0

| accepted

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...

bijna 2 jaar 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,...

ongeveer 2 jaar 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...

ongeveer 2 jaar 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))...

ongeveer 2 jaar 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

ongeveer 2 jaar 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 ...

ongeveer 2 jaar ago | 0

| accepted

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)...

ongeveer 2 jaar 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...

meer dan 2 jaar ago | 0

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

meer dan 2 jaar ago | 0

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

meer dan 2 jaar 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.

meer dan 2 jaar ago | 0

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

meer dan 2 jaar ago | 0

| accepted

Submitted


aux2bib
BibTex (LaTeX) sublibrary from an AUX file

meer dan 2 jaar 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 ...

meer dan 2 jaar 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...

meer dan 2 jaar 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 ...

meer dan 2 jaar 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...

meer dan 2 jaar ago | 0

| accepted

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...

meer dan 2 jaar 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...

meer dan 2 jaar ago | 1

| accepted

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...

meer dan 2 jaar ago | 0

| accepted

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...

meer dan 2 jaar 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...

meer dan 2 jaar ago | 0

| accepted

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...

meer dan 2 jaar ago | 0

| accepted

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

meer dan 2 jaar ago | 0

Submitted


aux2bib
BibTex sublibrary from a LaTeX AUX file

meer dan 2 jaar 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)

meer dan 2 jaar ago | 0

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