Question

LU decomposition algorithm change

For this particular example: A=[ 1 2 3; 4 5 6; 7 8 9; 10 11 12]; I get two different results depending on...

11 months ago | 2 answers | 0

Answered

Inserting a double to a cell

E.g., x = randi(100,10,10) % sample data columns = [4,7]; % columns to check minx = min(x(:,columns)) % minimum of the two co...

Inserting a double to a cell

E.g., x = randi(100,10,10) % sample data columns = [4,7]; % columns to check minx = min(x(:,columns)) % minimum of the two co...

11 months ago | 0

| accepted

Answered

Using Matlab to solve 1D Schrödinger Equation (Strange Eigenfunctions)

Python: return is misspelled retrun The mL2V( ) function returns 1000*(y-1/2)**2 I don't see where y is defined prior to the ...

Using Matlab to solve 1D Schrödinger Equation (Strange Eigenfunctions)

Python: return is misspelled retrun The mL2V( ) function returns 1000*(y-1/2)**2 I don't see where y is defined prior to the ...

11 months ago | 0

Answered

1×0 empty double row vector using find

Welcome to the world of floating point arithmetic. For your specific example, they are not equal. E.g., x=[0 0.1 0.2 0.3 0.4 0....

1×0 empty double row vector using find

Welcome to the world of floating point arithmetic. For your specific example, they are not equal. E.g., x=[0 0.1 0.2 0.3 0.4 0....

11 months ago | 1

Answered

How to plot the first derivative of solution?

After the ode45( ) call, simply pass your x solution through your derivative function to obtain the xdot values. You can either ...

How to plot the first derivative of solution?

After the ode45( ) call, simply pass your x solution through your derivative function to obtain the xdot values. You can either ...

11 months ago | 0

Answered

optimizing: fastest way to detect if ANY points are within distance N of points?

Here is a naive brute force mex routine you can try out. It makes no attempts at cache optimization or multi-threading, and is p...

optimizing: fastest way to detect if ANY points are within distance N of points?

Here is a naive brute force mex routine you can try out. It makes no attempts at cache optimization or multi-threading, and is p...

11 months ago | 0

Answered

"roots" call is not providing the correct answer

Rename your old roots file (preferred method) or move it to a directory that is not on the MATLAB path. That way it won't shadow...

"roots" call is not providing the correct answer

Rename your old roots file (preferred method) or move it to a directory that is not on the MATLAB path. That way it won't shadow...

11 months ago | 1

Answered

How can ı solve this error ??Unable to perform assignment because the size of the left side is 1-by-5 and the size of the right side is 26-by-1.

You could expand the size of the LHS array. E.g., poles_real(i, 1:numel(roots_poly)) = real(roots_poly); poles_imag(i,...

How can ı solve this error ??Unable to perform assignment because the size of the left side is 1-by-5 and the size of the right side is 26-by-1.

You could expand the size of the LHS array. E.g., poles_real(i, 1:numel(roots_poly)) = real(roots_poly); poles_imag(i,...

11 months ago | 0

Answered

angle of a vector centered at a certain point

Once you have the vectors, you can calculate the angles between the vectors using the technique I posted here: https://www.math...

angle of a vector centered at a certain point

Once you have the vectors, you can calculate the angles between the vectors using the technique I posted here: https://www.math...

11 months ago | 0

Answered

How to expand dimension of a 2D array

All MATLAB trailing singleton (1) dimensions beyond the 2nd dimension are not physically stored, and will not show up in a size(...

How to expand dimension of a 2D array

All MATLAB trailing singleton (1) dimensions beyond the 2nd dimension are not physically stored, and will not show up in a size(...

11 months ago | 2

Answered

A single precision matrix multiplication problem

Somewhat related side comments: In general, the BLAS/LAPACK libraries do not contain mixed type argument routines. E.g., there ...

A single precision matrix multiplication problem

Somewhat related side comments: In general, the BLAS/LAPACK libraries do not contain mixed type argument routines. E.g., there ...

11 months ago | 2

Answered

How is this even logical?

When assigning into rows or columns via indexing, MATLAB will conform a RHS vector from row or column to row or column if necess...

How is this even logical?

When assigning into rows or columns via indexing, MATLAB will conform a RHS vector from row or column to row or column if necess...

11 months ago | 0

Answered

Matlab crashes when running a specific Fortan MEX file under MacOS

The MATLAB Fortran API interface needs to be treated as a pass-by-reference interface. That means you need to have the exact typ...

Matlab crashes when running a specific Fortan MEX file under MacOS

The MATLAB Fortran API interface needs to be treated as a pass-by-reference interface. That means you need to have the exact typ...

11 months ago | 0

Answered

What does [n==0] means?

Try it out and see: n = 3; N = 3; n == 0 n == N n = randi(4,1,10) - 1 n == 0 n == N Returns logical true/false where val...

What does [n==0] means?

Try it out and see: n = 3; N = 3; n == 0 n == N n = randi(4,1,10) - 1 n == 0 n == N Returns logical true/false where val...

12 months ago | 0

Answered

How to update a symmetric matrix?

E.g., M = rand(6)<0.3; M = double(logical(M+M')) % an arbitrary symmetric matrix VarMin= 1; % Lower Bound of Variables...

How to update a symmetric matrix?

E.g., M = rand(6)<0.3; M = double(logical(M+M')) % an arbitrary symmetric matrix VarMin= 1; % Lower Bound of Variables...

12 months ago | 0

| accepted

Answered

Recursive Method returning answers backwards

This is a very convoluted way to program the Euler method. There is no need for recursion here, just use simple loops instead. ...

Recursive Method returning answers backwards

This is a very convoluted way to program the Euler method. There is no need for recursion here, just use simple loops instead. ...

12 months ago | 1

| accepted

Answered

How to randomize order of functions

E.g., Using the cell array approach with randperm: function [results] = runTests(testparameters) f = {@test1,@test2,@test3,@te...

How to randomize order of functions

E.g., Using the cell array approach with randperm: function [results] = runTests(testparameters) f = {@test1,@test2,@test3,@te...

12 months ago | 0

| accepted

Answered

eval() is too slow to numerically evaluate a function with X(t) and Y(t).

Something like this? syms X(t) Y(t) Vfun = [2*X + Y ; cos(X)*X^2 + Y^3 ; 3 + sin(Y)] syms x y vfun = subs(Vfun,[X Y],[x y])...

eval() is too slow to numerically evaluate a function with X(t) and Y(t).

Something like this? syms X(t) Y(t) Vfun = [2*X + Y ; cos(X)*X^2 + Y^3 ; 3 + sin(Y)] syms x y vfun = subs(Vfun,[X Y],[x y])...

12 months ago | 0

| accepted

Answered

I have one column data 57600 points, how can i convert it to 240 by 240 matrix!

x = your column vector result = reshape(x,240,240); or you might need the transpose: result = reshape(x,240,240).';

I have one column data 57600 points, how can i convert it to 240 by 240 matrix!

x = your column vector result = reshape(x,240,240); or you might need the transpose: result = reshape(x,240,240).';

12 months ago | 0

Answered

I want to calculate pi^2 to 22 decimal places

You can use this excellent FEX submission by John D'Errico: https://www.mathworks.com/matlabcentral/fileexchange/36534-hpf-a-bi...

I want to calculate pi^2 to 22 decimal places

You can use this excellent FEX submission by John D'Errico: https://www.mathworks.com/matlabcentral/fileexchange/36534-hpf-a-bi...

1 year ago | 2

Answered

How to stop running code once conditions are met?

If your Birthday function is supposed to represent only one trial (a reasonable thing to do), then you should be returning n, no...

How to stop running code once conditions are met?

If your Birthday function is supposed to represent only one trial (a reasonable thing to do), then you should be returning n, no...

1 year ago | 0

Answered

How to fix the must be a column vector error?

You should double check your derivative function. Shouldn't the result be a 4-element column vector that is a function of q? Ne...

How to fix the must be a column vector error?

You should double check your derivative function. Shouldn't the result be a 4-element column vector that is a function of q? Ne...

1 year ago | 0

Answered

How to compare elements of two vectors in MATLAB ?

Compare for what purpose? E.g., these statements will compare them: isequal(v1,v2) % are they equal v1 == v2 % matrix of indi...

How to compare elements of two vectors in MATLAB ?

Compare for what purpose? E.g., these statements will compare them: isequal(v1,v2) % are they equal v1 == v2 % matrix of indi...

1 year ago | 0

Answered

Problem with time steps in Runge-Kutte method

"... I get different results with different time steps ..." In general, that is the expected result. I suppose the real questi...

Problem with time steps in Runge-Kutte method

"... I get different results with different time steps ..." In general, that is the expected result. I suppose the real questi...

1 year ago | 1

Answered

angle2dcm: How to reference direction cosine matrix output?

Does this do what you want: x = zeros(1,m); % reorder these to row vectors y = zeros(1,m); z = zeros(1,m); : xyz = [x;y;z];...

angle2dcm: How to reference direction cosine matrix output?

Does this do what you want: x = zeros(1,m); % reorder these to row vectors y = zeros(1,m); z = zeros(1,m); : xyz = [x;y;z];...

1 year ago | 0

| accepted

Answered

Motion equation of a space engin in low earth orbit

As Bjorn has pointed out, your J2 terms are all the same but they should be different because the equatorial bulge affects the z...

Motion equation of a space engin in low earth orbit

As Bjorn has pointed out, your J2 terms are all the same but they should be different because the equatorial bulge affects the z...

1 year ago | 1

Answered

Problem using 4th order Runge-Kutta method

You have a factor of 2*K4 that shouldn't be there. It should just be K4. E.g., Fx = @(t,x,vx,y,vy,z,vz) [vx; 3*t; vy; t; vz; 7*...

Problem using 4th order Runge-Kutta method

You have a factor of 2*K4 that shouldn't be there. It should just be K4. E.g., Fx = @(t,x,vx,y,vy,z,vz) [vx; 3*t; vy; t; vz; 7*...

1 year ago | 0

Answered

How can I find angle between two vectors in 3D ranging from 0 to 360 or -180 to +180?

https://www.mathworks.com/matlabcentral/answers/501449-angle-betwen-two-3d-vectors-in-the-range-0-360-degree

How can I find angle between two vectors in 3D ranging from 0 to 360 or -180 to +180?

https://www.mathworks.com/matlabcentral/answers/501449-angle-betwen-two-3d-vectors-in-the-range-0-360-degree

1 year ago | 0

Answered

Add another column to the right end of this array

your_matrix(:,end+1) = 1.5;

Add another column to the right end of this array

your_matrix(:,end+1) = 1.5;

1 year ago | 0