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...

4 days 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...

4 days 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

4 days 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...

5 days 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)));

5 days 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;

1 month 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...

2 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...

2 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...

2 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/

2 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...

2 months ago | 1

| 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 = ...

3 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

3 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 ./

3 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...

3 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 ...

3 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...

3 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...

3 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); ...

3 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

3 months ago | 0

| accepted

Answered

Area under curves with different length (trapz)

If you have the x axes for both waves, it is pretty easy to use trapz: N1 = 1036; N2 = 9958; % wave 1 x1 = linspace(0,2*pi...

Area under curves with different length (trapz)

If you have the x axes for both waves, it is pretty easy to use trapz: N1 = 1036; N2 = 9958; % wave 1 x1 = linspace(0,2*pi...

3 months ago | 1

| accepted

Answered

Plotting the integral of a graph

Suppose that x and y are the vectors defining your waveform. % dummy values x = linspace(0,2*pi,1000); y = sin(x); % integ...

Plotting the integral of a graph

Suppose that x and y are the vectors defining your waveform. % dummy values x = linspace(0,2*pi,1000); y = sin(x); % integ...

3 months ago | 1

| accepted

Answered

Does anybody know how to write a function which returns the coordinates of a convex hull of a list of certain points?

% your data N = 20; List = rand(N,2); % convex hull (k is the pointer to the rows in List with the convex hull k = convhul...

Does anybody know how to write a function which returns the coordinates of a convex hull of a list of certain points?

% your data N = 20; List = rand(N,2); % convex hull (k is the pointer to the rows in List with the convex hull k = convhul...

3 months ago | 0

Answered

How to divide a part of array to the another part of it?

T = psi2(1:5)./psi(end-4:end);

How to divide a part of array to the another part of it?

T = psi2(1:5)./psi(end-4:end);

3 months ago | 0

| accepted

Answered

How can speed up the blow codes?

Edit: added attempt for ncount I don't understand what ncount is doing, it looks like a counter but I don't understand why you ...

How can speed up the blow codes?

Edit: added attempt for ncount I don't understand what ncount is doing, it looks like a counter but I don't understand why you ...

3 months ago | 0

Answered

Array indices must be positive integers or logical values

Your index k starts from 0 and you are indexing h with k, so you are asking at the first iteration h(0). Matlab has 1-indexing s...

Array indices must be positive integers or logical values

Your index k starts from 0 and you are indexing h with k, so you are asking at the first iteration h(0). Matlab has 1-indexing s...

3 months ago | 0

Answered

while loop performance improvement

I don't know the starting value of k, assuming it is 1 idx = 1:rate:period mysum = sum(array(idx,2)); % note that sum is the n...

while loop performance improvement

I don't know the starting value of k, assuming it is 1 idx = 1:rate:period mysum = sum(array(idx,2)); % note that sum is the n...

3 months ago | 1

| accepted

Answered

Euler method error in code Index exceeds the number of array elements (1). in my my code

Checking the sintax of the code only I see 3 issues 1) In the for loop you wrote a(400-x(n)), that is you are addressing the po...

Euler method error in code Index exceeds the number of array elements (1). in my my code

Checking the sintax of the code only I see 3 issues 1) In the for loop you wrote a(400-x(n)), that is you are addressing the po...

3 months ago | 1

| accepted

Answered

Population growth in 7 years

% rate r = 0.0063; % years t = 7; % initial population a = 5e6; % population y = a*(1+r)^t

Population growth in 7 years

% rate r = 0.0063; % years t = 7; % initial population a = 5e6; % population y = a*(1+r)^t

3 months ago | 2

| accepted