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Vladimir Sovkov


Last seen: 1 day ago

St. Petersburg State University

70 total contributions since 2014

Professional Interests: computational physics, applied mathematics

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

1 day ago | 0

| accepted

Submitted


aux2bib
BibTex (LaTeX) sublibrary from an AUX file

8 days ago | 0 downloads |

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 ...

8 days 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...

11 days 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 ...

12 days 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...

12 days 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...

13 days 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...

13 days 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...

19 days 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...

19 days 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...

29 days 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...

1 month 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

1 month ago | 0

Submitted


aux2bib
BibTex sublibrary from a LaTeX AUX file

1 month 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)

2 months ago | 0

Answered
How to Convert 3d matrix to row matrix???
a=rand(2,2,2) % a sample 3D matrix a b=a(:)' % is turned to the 1D row matrix b

4 months ago | 2

Answered
Plot the trapeoidal waveform using given equations
syms theta y=piecewise(... 0<=theta<2*pi/3,1,... 2*pi/3<=theta<pi,(1-6/pi*(theta-2*pi/3)),... pi<=theta<5*pi/3,-...

5 months ago | 0

Answered
How to draw an ellipse
The code discussed at https://www.mathworks.com/matlabcentral/answers/497966-how-to-find-the-vertical-height-of-an-ellipse-y-axi...

6 months ago | 0

Answered
Eigenvalues corresponds to eigenvectors
Absolutely standard: L(k,k) ~ V(:,k). You can check it with the code: for k=1:size(h,1) disp(strcat('k=',num2str(k),'; h*v-la...

6 months ago | 0

| accepted

Answered
Subs Command for Multivariable Function
If e^ is the exponent and if you want to estimate the result numerically (from the question it is not quite clear what you want)...

6 months ago | 0

Answered
Partial least-squares regression evalutaion
The equation considered in PLS of Matlab is rather Y = X(:,:)*B(2:end,:) + repmat( B(1,:),n,1 ) + E, where: X is an n-by-...

6 months ago | 0

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Answered
Normalization of complex eigenvector
You probably want V(:,1) = V(:,1)/norm(V(:,1)); Besides, if your theta and phi are supposed to be real, the overall computatio...

6 months ago | 0

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Answered
Eigenvector without calling eigenvalues
This is not an error but a warning that you do not use the eigenvalues, which influences nothing. If you want to avoid it, subst...

6 months ago | 0

Answered
Can I check if factored and expanded polynomial forms are equal?
simplify((w^2-k^2) - (w+k)*(w-k)) ans = 0 expand((w+k)*(w-k)) ans = w^2 - k^2 factor(w^2-k^2) ans = [ -1, k - w...

6 months ago | 0

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Answered
How to call some object handle from opening function of figure?
u0=findobj('Tag','lst1','Style','listbox','Parent',gcf); % search for all the object properties you used to identify it set(u0,...

6 months ago | 0

| accepted

Submitted


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

6 months ago | 8 downloads |

Answered
Find orthogonal complement for given matrix
B=null(A'); The matrix transposing is important!

6 months ago | 1

| accepted

Answered
How can I write a loop, which can make the parameter "V" change with a cyclic variable "i"?
Use Matlab functions "strcat" and "num2str" within a loop.

7 months ago | 0

| accepted

Answered
How do I calculate acceleration with velocity and the code given?
% sample data t=0:0.1:10; % time x=3+2*t+t.^2; % coordinate [t,ind]=sort(t); % in a case time is not in an ascending order ...

7 months ago | 0

Answered
How to assign numbers to letters of the alphabet. Ex. A/a=1 B/b=2
The ASCII codes can be found with the function double double('A'); 65 If you want to get its ordinal number in the alphabet, ...

7 months ago | 0

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