Answered

How to change a column vector into a square a matrix?

Not as elegant as it could be but it works, especially for small matrices % matrix dimension n = 3; % your entries (here du...

How to change a column vector into a square a matrix?

Not as elegant as it could be but it works, especially for small matrices % matrix dimension n = 3; % your entries (here du...

15 days ago | 0

Answered

Calculate acceleration from velocity and time fron excel

acceleration = diff(data.Velocity)./diff(data.Time); Note that this vector has one entry less than the original ones, so you ma...

Calculate acceleration from velocity and time fron excel

acceleration = diff(data.Velocity)./diff(data.Time); Note that this vector has one entry less than the original ones, so you ma...

1 month ago | 0

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Answered

Subscripted assignment dimension mismatch.

You can use repmat and create a char array function bigstring = string_multiplication(str,N) bigstring = repmat(str,N,1); ...

Subscripted assignment dimension mismatch.

You can use repmat and create a char array function bigstring = string_multiplication(str,N) bigstring = repmat(str,N,1); ...

2 months ago | 0

Answered

Simulation errors when multiplying matrices

I start a new clean answer You don't have to use the index i inside your matrix like you are doing in your code: in that way yo...

Simulation errors when multiplying matrices

I start a new clean answer You don't have to use the index i inside your matrix like you are doing in your code: in that way yo...

3 months ago | 0

Answered

Solving Complex Matrix Operations

You can do this in a for loop or using arrayfun % your A vector A = rand(1,1001); % dummy vector % calculation of the matr...

Solving Complex Matrix Operations

You can do this in a for loop or using arrayfun % your A vector A = rand(1,1001); % dummy vector % calculation of the matr...

3 months ago | 0

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Answered

Replicate values in a matrix i-1 times

Quick and dirty for loop A=[1; 4; 8; 3; 2; 6] B = []; for i = 1:length(A) B = [B; repmat(A(i),i,1)]; end You can als...

Replicate values in a matrix i-1 times

Quick and dirty for loop A=[1; 4; 8; 3; 2; 6] B = []; for i = 1:length(A) B = [B; repmat(A(i),i,1)]; end You can als...

3 months ago | 0

Answered

Find independent variables that minimize function

If you have only lower and upper bounds, use them directly in fmincon % your function fun = @(x) ((x(1)-real(0.5*(x(1)-(sqrt(x...

Find independent variables that minimize function

If you have only lower and upper bounds, use them directly in fmincon % your function fun = @(x) ((x(1)-real(0.5*(x(1)-(sqrt(x...

3 months ago | 0

| accepted

Answered

Simulation errors when multiplying matrices

Inside the loop in the first instruction Vn(:,i) is 5x1 but T is 5x5. Matlab now (starting in 2016, I guess) implicitly expands ...

Simulation errors when multiplying matrices

Inside the loop in the first instruction Vn(:,i) is 5x1 but T is 5x5. Matlab now (starting in 2016, I guess) implicitly expands ...

3 months ago | 0

Answered

Weighted fit using fmincon

How about to repeat the samples of the points you want to weight more?

Weighted fit using fmincon

How about to repeat the samples of the points you want to weight more?

3 months ago | 0

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Answered

how to find the optimal value of a matrix that minimize a function?

If I understand correctly the problem can be recast to the following A*W = B*H = F; [a11 a12; a21 a22]*[w1 w2 0 0; 0 0 w3 w4] ...

how to find the optimal value of a matrix that minimize a function?

If I understand correctly the problem can be recast to the following A*W = B*H = F; [a11 a12; a21 a22]*[w1 w2 0 0; 0 0 w3 w4] ...

3 months ago | 0

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Answered

plot 2 3D vectors in Matlab

% vectors a = [1 2 -3]; b = [-3 12 -13]; % starting point C0 = [0 0 0]; % put vector in a matrix, to make the code more...

plot 2 3D vectors in Matlab

% vectors a = [1 2 -3]; b = [-3 12 -13]; % starting point C0 = [0 0 0]; % put vector in a matrix, to make the code more...

3 months ago | 0

Answered

Error using sparse Index into matrix must be positive.

Simply remove "-1" from the definition of R. randi returns pseudorandom integers between 1 and the first inupt. The entries of C...

Error using sparse Index into matrix must be positive.

Simply remove "-1" from the definition of R. randi returns pseudorandom integers between 1 and the first inupt. The entries of C...

3 months ago | 0

Answered

How to solve time and space deriavtive using ode45?

Have a look at pdepe: it solves 1-D parabolic and elliptic PDEs

How to solve time and space deriavtive using ode45?

Have a look at pdepe: it solves 1-D parabolic and elliptic PDEs

3 months ago | 0

Answered

Finite Difference Matrix Help

Edit: I changed my answer including a reference and the second order derivative The coefficients for central differences of dif...

Finite Difference Matrix Help

Edit: I changed my answer including a reference and the second order derivative The coefficients for central differences of dif...

3 months ago | 0

Answered

improved Euler integration scheme (possible code error) in matlab

I think it should be "-" p(1) = (-z(1)*(1-(z(2)))); p(2) = z(2)*(1-(z(1)));

improved Euler integration scheme (possible code error) in matlab

I think it should be "-" p(1) = (-z(1)*(1-(z(2)))); p(2) = z(2)*(1-(z(1)));

3 months ago | 0

Answered

Make entries of first row and column of matrix all equal to zero.

% nullify first col B(:,1) = 0; %nullify first row B(1,:) = 0;

Make entries of first row and column of matrix all equal to zero.

% nullify first col B(:,1) = 0; %nullify first row B(1,:) = 0;

4 months ago | 0

Answered

plot vector using complex numbers

You can use compass or quiver % your matrix A = [-3+4i;-2+5i;1+3i;6+2i;-1-8i]; % with compass figure compass(real(A),imag...

plot vector using complex numbers

You can use compass or quiver % your matrix A = [-3+4i;-2+5i;1+3i;6+2i;-1-8i]; % with compass figure compass(real(A),imag...

5 months ago | 0

Answered

constantly receiving an error undefined function or variable z when use solve

Polynomials with a degree greater than 4 do not have explicit solutions. You can use vpa syms x y f1 = y == x^3 f2 = x^2+y^2...

constantly receiving an error undefined function or variable z when use solve

Polynomials with a degree greater than 4 do not have explicit solutions. You can use vpa syms x y f1 = y == x^3 f2 = x^2+y^2...

5 months ago | 0

Answered

How to multiply only some column and rows for a given number?!

You are close to the answer, but you need to keep the first column % your matrix with data A = rand(2,21); % multiply all b...

How to multiply only some column and rows for a given number?!

You are close to the answer, but you need to keep the first column % your matrix with data A = rand(2,21); % multiply all b...

5 months ago | 1

Answered

Unstable derivative approximation when steps get too small

This is expected. Look here for details https://blogs.mathworks.com/cleve/2013/10/14/complex-step-differentiation/

Unstable derivative approximation when steps get too small

This is expected. Look here for details https://blogs.mathworks.com/cleve/2013/10/14/complex-step-differentiation/

5 months ago | 1

Answered

How to start streamlines on the surface of a sphere? griddedInterpolant requires at least two sample points in each dimension

It looks like streamline does not accepts coordinates coming from your spherical construction. If you start form a cartesian gri...

How to start streamlines on the surface of a sphere? griddedInterpolant requires at least two sample points in each dimension

It looks like streamline does not accepts coordinates coming from your spherical construction. If you start form a cartesian gri...

5 months ago | 2

| accepted

Answered

n! permutation matrices

Is this what you wish? % identity matrix A = eye(4); % permuatations idx = perms(1:4); % all matrices in a cell array B = ...

n! permutation matrices

Is this what you wish? % identity matrix A = eye(4); % permuatations idx = perms(1:4); % all matrices in a cell array B = ...

6 months ago | 0

Answered

Solve the system of the 1-st order differential equations

Have a look at the ode suite

Solve the system of the 1-st order differential equations

Have a look at the ode suite

6 months ago | 0

Answered

How to make two vectors the same size?

Try fkld=sum(dot(p,log(p./q))); with the element-wise division ./

How to make two vectors the same size?

Try fkld=sum(dot(p,log(p./q))); with the element-wise division ./

6 months ago | 1

| accepted

Answered

Inner matrix dimensions must agree

fkj= sum(.5*((p.^2-q.^2).^2)./((p.*q).^1.5)); Note that .^ .* and ./ operators are used for element-wise operation (see also St...

Inner matrix dimensions must agree

fkj= sum(.5*((p.^2-q.^2).^2)./((p.*q).^1.5)); Note that .^ .* and ./ operators are used for element-wise operation (see also St...

6 months ago | 1

| accepted

Answered

Inverse matrix in Matlab very different to Excel

The answer is not very different. As Jeremy commented, the results are similar a part from numerical tolerances. You can verify ...

Inverse matrix in Matlab very different to Excel

The answer is not very different. As Jeremy commented, the results are similar a part from numerical tolerances. You can verify ...

6 months ago | 1

| accepted

Answered

How to call a multi output function without repeating the run

function [c, ceq] = nonconst(x) [total_value, Delta_value, energy_value] = digital(x); c = total_value-u*v;... ` `%fi...

How to call a multi output function without repeating the run

function [c, ceq] = nonconst(x) [total_value, Delta_value, energy_value] = digital(x); c = total_value-u*v;... ` `%fi...

6 months ago | 0

| accepted

Answered

How to color a mesh by temperature(or other value) preserving the elevation. Using two matrix(same length)

% dummy data [X,Y] = meshgrid(1:0.5:10,1:20); Z = sin(X).*cos(Y); T = X+Y; % plot surf(X,Y,Z,T) colormap('hot') colorba...

How to color a mesh by temperature(or other value) preserving the elevation. Using two matrix(same length)

% dummy data [X,Y] = meshgrid(1:0.5:10,1:20); Z = sin(X).*cos(Y); T = X+Y; % plot surf(X,Y,Z,T) colormap('hot') colorba...

6 months ago | 1

| accepted

Answered

How can I get an array of velocity if I have an array of position and another array of time

First, you need a element-wise division pos = [0 2 4 8 16 32 64]; t = [0 0.1 0.2 0.3 0.4 0.5 0.6]; V = diff(pos)./diff(t); ...

How can I get an array of velocity if I have an array of position and another array of time

First, you need a element-wise division pos = [0 2 4 8 16 32 64]; t = [0 0.1 0.2 0.3 0.4 0.5 0.6]; V = diff(pos)./diff(t); ...

6 months ago | 0

| accepted

Answered

Numerical Solution for a System of THREE Differential Equations

This is an ODE, not PDE. Look for the ODE suite

Numerical Solution for a System of THREE Differential Equations

This is an ODE, not PDE. Look for the ODE suite

6 months ago | 0

| accepted