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how to check if two symbolic fractions are the same?
syms x y z fraction1 = (x+y)/(x*y) + z; fraction2 = (x+y+x*y*z)/(x*y); isAlways(fraction1==fraction2)

約3年前 | 1

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Problem when using pdepe with time dependant and nonconsistent boundary conditions
If you specify the gradients of the solution variables as boundary conditions (as you do in your boundary function), you cannot ...

約3年前 | 0

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Computing expint(x), where x is an array, locks up for some x but not others that are very similar
The computation of the second column is even faster. I wonder how matlab evaluates expint(x) if x is a vector different from eva...

約3年前 | 0

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Error L2 is not defined
Since g does not depend on w and f does not depend on z, the equations are not coupled and you can do it in the following manner...

約3年前 | 0

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Problems in finding a set of global minima
L=1; L1=L/6; omega0 = 0; omegaR = 10; tR= (2*pi)/omegaR; te = 0.8; t1 = 0; t_i = te/50; gamma_i = 1; %alpha = (t_i^2)/...

約3年前 | 1

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NaN computed by model function, fitting cannot continue. Try using or tightening upper and lower bounds on coefficients.
a11 and a12 must be such that a11*C1 + a12*C2 > 0. Otherwise, the operation ^(n1-1) gives a complex result. The simplest exampl...

約3年前 | 0

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Skipping Iterations in a For Loop
FEM = [-16 16 -18 12 -6 6]; n = numel(FEM); for i = 1:n-3 FEM(i+1) + FEM(i) end FEM(end) + FEM(end-1)

約3年前 | 0

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Finding Extremum of Multivariate Functions
R(1,2)=0.7844; R(1,3)=0.7844; R(2,2)=0.6202; R(2,3)=-0.2021; R(3,3)=0.5864; x0 = 0.5*ones(10,1); lb = -1*ones(10,1); ub ...

約3年前 | 1

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Problem in solving a Fokker-Planck equation
The order of your loops is wrong. Try Nx=100;Ny=100;Nt=1000; xmin=0;xmax=3; ymin=0;ymax=3; dx=(xmax-xmin)/(Nx-1); dy=(ymax-...

約3年前 | 0

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What is the difference between "no feasible solution found" and "the problem is infeasible" messages in LSQLIN?
"No feasible solution found" means: there might be a feasible solution for your problem, but I was not able to find it. But I gi...

約3年前 | 1

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Strange temperature output for 2D heat equation
% Material properties rho=7850; Lambda=50; cp=477; alpha=Lambda/(rho*cp); % Geometry and mesh L = 0.1; nx = 10; ny = n...

約3年前 | 1

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Getting very large numbers for solutions of a system of equation
syms x y z q r theta_0 = 0; beta = 0.5; U=exp(2*i*theta_0); eqn1 = (U*beta*besselj(0,2)-1)*x + (U*beta*besselj(1,2))*y + (...

約3年前 | 0

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error in running my optimization code
I assume that "yexpected" is a matrix of size 49x3. yexpected=table2array(Book65); p0 = [3 25 25 12 1 0.5 1]; sol = lsqnonlin...

約3年前 | 0

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How can to compute the following case?
D = load("D.mat"); D = D.D; n = size(D,1); m = size(D,2); distance = zeros(n,m,n,m); for i=1:n for j=1:m ...

約3年前 | 1

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Plot a nx2 matrix as points
A=[0.5 2; 1.0 -0.8; 1.5 -2.5]; plot(A(:,1),A(:,2),'o')

約3年前 | 0

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Solve two equations for one variable
syms P_st vdq_st_abs Vabs delta_st Vangle Xg Q_st real eq1 = P_st - vdq_st_abs * Vabs * sin(delta_st - Vangle) / Xg == 0; eq2 ...

約3年前 | 0

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non linear regression problem. fitnlm gives error
Look at the values of K and B. Do you really want to approximate B by a*K^b ? format long K = load("FITDATAK.mat"); K = K.FIT...

約3年前 | 0

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Am I doing thid correct. pdepe function
x = 0:0.1:1; t = 0:0.05:0.5; m = 0; u = pdepe(m,@PDEeqn1,@initial1,@bc1,x,t); plot(x,[u(1,:);u(2,:);u(3,:);u(4,:);u(end,:)])...

約3年前 | 0

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How to solve coupled systems of PDEs and ODEs using method of lines
http://www.scholarpedia.org/article/Method_of_lines/example_implementation https://www.sciencedirect.com/science/article/abs/pi...

約3年前 | 0

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integral2 for a non-scalar matlabFunction
"intagrand_temp" is a 5x3 matrix of symbolic functions in eta and zi. I don't understand which scalar-valued function(s) you wan...

約3年前 | 1

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How to check the degree of parallelism
The intersection of P1 and P2 is given by x = origin1 + directions1*lambda the intersection of P1 and P3 is given by x = orig...

約3年前 | 1

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Hi i have created a code for adsorption process breakthrough curve following one of the examples, however i still have some orange cations around please help
You solve in q, not in qstar. Thus q=y(Nz+1:2*Nz); instead of qstar=y(Nz+1:2*Nz); Further, I doubt that qstar(i)=qm.*ks.*c...

約3年前 | 0

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Error with ode45 in line 89. Trying to use ode 45 to give data on a 4x4 state space matrix
M1=1; M2=1; K1=2; K2=2; B1=1; B2=1; x1_0=1; v1_0=1; x2_0=0; v2_0=1; %% equations q0=[ x1_0 v1_0 x2_0 v2_0]; dQdt = ...

約3年前 | 0

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How to use fminbnd but with multiple variables
In the case above, your objective function is separable in the optimization variables. Thus you can solve two independent proble...

約3年前 | 1

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How can I obtain all possible combinations of 3 decimals whose sum equals 1, without running into memory and space issues?
If you have some time, you can try I = 0:0.001:1. Why don't you use the code from the File Exchange ? I = 0:0.01:1; n = num...

約3年前 | 0

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Help creating an array with uniformly distributed random numbers (row-wise) comprised between 0 and 1, with each column having a sum of 1
https://uk.mathworks.com/matlabcentral/fileexchange/9700-random-vectors-with-fixed-sum You cannot expect the usual uniform dist...

約3年前 | 1

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How can I input sum over in function depend on time?
Never make changes in the RK4 function. Changes have to be made in the call to RK4 and in f. tstart = 0; tend = 100; dt = 0....

約3年前 | 0

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Solving stokes flow use pde toolbox
The (simplified) Navier-Stokes equations need a special numerical treatment and cannot be solved by a general-purpose code like ...

約3年前 | 2

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How do i fix the error that i am getting?
Remove the semicolon behind the line pivotColumns = rrefA(:,1:end-1); execute the code and see if it makes sense to insert the...

約3年前 | 0

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try to find hessian matrix
The vector of independent variables is (x1,x2,...,xn): syms i k n = 3; x = sym('x',[1 n]) f = n*log(k) - n*log(1/n*sum(x.^k)...

約3年前 | 0