# Vladimir Sovkov

### St. Petersburg State University

Professional Interests: computational physics, applied mathematics

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**Content Feed**

How do I uninstall MATLAB 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 days ago | 0

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...

11 months ago | 0

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How to average columns of matrix without loop?

reshape(mean(reshape(A',n,[]))',size(A,2)/n,[])'

11 months ago | 0

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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...

12 months ago | 1

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,...

1 year ago | 0

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...

1 year ago | 1

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 year ago | 1

make different numbers with the same digits

x=1342; y=str2num(sort(num2str(x),'ascend')); % smaller z=str2num(sort(num2str(x),'descend')); % bigger

1 year ago | 0

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 ...

1 year ago | 0

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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)...

1 year ago | 0

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...

1 year ago | 0

How can I create a script that calculates this combinatorial?

C=nchoosek(n,r)

1 year ago | 0

Specify eigenvector for eigs

Matlab documentation: 'StartVector' — Initial starting vector random vector (default) | vector Initial starting vector, spe...

1 year ago | 0

How to "wrap text" on pushbutton string?

Use the cell array with entries containing text fragments to be shown in separate strings.

1 year ago | 0

how to implement the algorithm for approximating Cosine using the Taylor series

syms theta n=4; taylor(cos(theta),'Order',n)

1 year ago | 0

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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 ...

1 year ago | 0

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...

1 year ago | 1

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 ...

1 year ago | 0

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...

1 year ago | 0

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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...

1 year ago | 0

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...

1 year ago | 1

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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...

1 year ago | 0

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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...

1 year ago | 0

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...

1 year ago | 0

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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 year ago | 0

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Debugging using external editor

https://www.mathworks.com/help/matlab/matlab_external/debugging-on-microsoft-windows-platforms.html

1 year ago | 0

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)

1 year ago | 0

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

1 year ago | 2

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,-...

2 years ago | 0

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...

2 years ago | 0