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Vladimir Sovkov


Last seen: 2 days ago

St. Petersburg State University

80 total contributions since 2014

Professional Interests: computational physics, applied mathematics

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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,...

30 days 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...

30 days 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))...

1 month 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

1 month 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 ...

2 months 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)...

2 months 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...

3 months ago | 0

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

3 months ago | 0

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

3 months 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.

3 months 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 months ago | 0

| accepted

Submitted


aux2bib
BibTex (LaTeX) sublibrary from an AUX file

4 months 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 ...

4 months 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 months 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 months 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 months 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 months 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 months 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...

4 months 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...

4 months 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...

5 months 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...

5 months 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

5 months ago | 0

Submitted


aux2bib
BibTex sublibrary from a LaTeX AUX file

5 months 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)

6 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

8 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,-...

9 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...

10 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...

10 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)...

10 months ago | 0

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