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Vladimir Sovkov


St. Petersburg State University

Last seen: 8 days 前 自 2014 起处于活动状态

Professional Interests: computational physics, applied mathematics

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已回答
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...

2 years 前 | 1

已回答
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...

3 years 前 | 0

| 已接受

已提交


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

3 years 前 | 7 次下载 |

已回答
How to average columns of matrix without loop?
reshape(mean(reshape(A',n,[]))',size(A,2)/n,[])'

3 years 前 | 0

| 已接受

已回答
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...

3 years 前 | 1

已回答
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,...

3 years 前 | 0

已回答
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...

3 years 前 | 1

已回答
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))...

3 years 前 | 1

已回答
make different numbers with the same digits
x=1342; y=str2num(sort(num2str(x),'ascend')); % smaller z=str2num(sort(num2str(x),'descend')); % bigger

3 years 前 | 0

已回答
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 ...

3 years 前 | 0

| 已接受

已回答
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)...

3 years 前 | 0

已回答
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 years 前 | 0

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

3 years 前 | 0

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

3 years 前 | 0

已回答
How to "wrap text" on pushbutton string?
Use the cell array with entries containing text fragments to be shown in separate strings.

3 years 前 | 0

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

3 years 前 | 0

| 已接受

已提交


aux2bib
BibTex (LaTeX) sublibrary from an AUX file

3 years 前 | 1 次下载 |

已回答
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 ...

3 years 前 | 0

已回答
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...

3 years 前 | 1

已回答
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 ...

3 years 前 | 0

已回答
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...

3 years 前 | 0

| 已接受

已回答
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...

3 years 前 | 0

已回答
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...

3 years 前 | 1

| 已接受

已回答
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...

3 years 前 | 0

| 已接受

已回答
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...

3 years 前 | 0

已回答
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...

3 years 前 | 0

| 已接受

已回答
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...

3 years 前 | 0

| 已接受

已回答
Debugging using external editor
https://www.mathworks.com/help/matlab/matlab_external/debugging-on-microsoft-windows-platforms.html

3 years 前 | 0

已提交


aux2bib
BibTex sublibrary from a LaTeX AUX file

3 years 前 | 0 次下载 |

已回答
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)

4 years 前 | 0

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