# Vladimir Sovkov

### St. Petersburg State University

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Professional Interests: computational physics, applied mathematics

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**Feeds**

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...

mer än 2 år ago | 2

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...

mer än 3 år ago | 0

| accepted

How to average columns of matrix without loop?

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

mer än 3 år 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...

mer än 3 år 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,...

mer än 3 år 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...

mer än 3 år 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))...

mer än 3 år 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

mer än 3 år 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 ...

mer än 3 år 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)...

mer än 3 år 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...

nästan 4 år ago | 0

How can I create a script that calculates this combinatorial?

C=nchoosek(n,r)

nästan 4 år ago | 0

Specify eigenvector for eigs

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

nästan 4 år ago | 0

How to "wrap text" on pushbutton string?

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

nästan 4 år ago | 0

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

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

nästan 4 år 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 ...

nästan 4 år 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...

nästan 4 år 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 ...

nästan 4 år 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...

nästan 4 år 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...

nästan 4 år 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...

nästan 4 år 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...

nästan 4 år 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...

nästan 4 år 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...

nästan 4 år 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...

nästan 4 år ago | 0

| accepted

Debugging using external editor

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

nästan 4 år 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)

nästan 4 år ago | 0