# Vladimir Sovkov

### St. Petersburg State University

Professional Interests: computational physics, applied mathematics

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**Content Feed**

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...

meer dan een jaar ago | 1

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...

meer dan 2 jaar ago | 0

| accepted

How to average columns of matrix without loop?

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

meer dan 2 jaar ago | 0

| accepted

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...

meer dan 2 jaar 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,...

meer dan 2 jaar 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...

meer dan 2 jaar 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))...

meer dan 2 jaar 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

meer dan 2 jaar 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 ...

meer dan 2 jaar ago | 0

| accepted

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)...

meer dan 2 jaar 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...

bijna 3 jaar ago | 0

How can I create a script that calculates this combinatorial?

C=nchoosek(n,r)

bijna 3 jaar ago | 0

Specify eigenvector for eigs

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

bijna 3 jaar ago | 0

How to "wrap text" on pushbutton string?

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

bijna 3 jaar ago | 0

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

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

bijna 3 jaar ago | 0

| accepted

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 ...

bijna 3 jaar 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...

bijna 3 jaar 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 ...

bijna 3 jaar 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...

bijna 3 jaar ago | 0

| accepted

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...

bijna 3 jaar 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...

bijna 3 jaar ago | 1

| accepted

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...

bijna 3 jaar ago | 0

| accepted

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...

bijna 3 jaar 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...

bijna 3 jaar ago | 0

| accepted

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...

bijna 3 jaar ago | 0

| accepted

Debugging using external editor

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

bijna 3 jaar 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)

bijna 3 jaar ago | 0