Community Profile # Alan Stevens

Last seen: Today 2020 이후 활성

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ODE45 returns NaN
t = 0 causes a problem. Try tspan = [0.1 100]; for example.

약 15시간 전 | 0

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How can I do an elliptic curve in Matlab?
Here's one simple way: % y^2 - y = x^3 - x % y = (1 +/- sqrt(4x^3 - 4x + 1))/2 n = 1000; x = -2:1/n:2; d = sqrt(4*x.^3-...

약 16시간 전 | 0

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Phase Portrait of ODE system
Do you mean something like this: % Part IIa. Base Case % Phase Portrait % % r=2.5; p=2; c=0.1; b=0.1; % % [x,v]=meshgr...

10일 전 | 0

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Plot with while loop
By the time you get to the plot command you only have a single value of t1 and a single value of y1 as you overwrite each of the...

17일 전 | 0

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How should I approach solving differential equation as function of two variables r, k?
You need to call the ode with something like [t, y] = ode45(@(t,y) deq(t,y,r,k),tVec,y0,r,k); where you pass values of r and k...

19일 전 | 1

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I need help plotting
More like this perhaps: Z1=500; Z2=50; Z3=500; u=1; tau1=(2*Z2)/(Z1+Z2); tau2=(2*Z1)/(Z1+Z2); tau3=(2*Z3)/(Z3+Z2); p1=(Z...

29일 전 | 1

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1D Heat Equation Explicit Scheme
Look at for i=1:(N) if (alpha*DELTA_t)/(DELTA_x^2)<=0.5 T(i,j+1)=T(i,j)+((alpha*DELTA_t)/((DELTA_x)^2))*(...

30일 전 | 1

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Solving a system of Second Order Equations
Not sure there is a symbolic solution, but it's easy enough to get a numerical one: tspan = [0 1]; % Start and end times % In...

약 1달 전 | 1

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How to solve 4th order Runge-Kutta for different initial conditions?
Here's a rather crude method (together with some corrections). You should be able to turn this into a much more elegant version...

약 1달 전 | 1

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1D Heat Equation Explicit Scheme (fixed)
With for i=0:0.1:50 you are trying to index variables with zero. However, Matlab's indexing starts at 1.

약 1달 전 | 1

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How to plot Homogeneous solution and Particular integral seperately of a second order differntial equation using ode45
ode45 just solves first order equations, so turn your second order equation into two first order ones, like so: y' = v v' = -4...

약 1달 전 | 0

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Trying to plot R_K 4th order, but keep getting straight line?
Check these equations F_sir = @(s,i,r) -a*s*i; % change the function as you desire G_sir = @(...

약 1달 전 | 1

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Not enough input arguments; fzero function
Replace T_mix = fzero(fun,T_mix_0); by T_mix = fzero(@fun,T_mix_0);

약 1달 전 | 1

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I am trying to use the trapezoidal rule to compute the flow rate of fluid through a pipe.
I think it needs to be more like this: % Velocity distribution function of the pipe % Area = pi*r^2 % dA = 2*pi*r dr % Q = V...

약 1달 전 | 0

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How to get area under the fit attained by Curve Fitting tool?
Try help trapz

약 1달 전 | 0

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Progressively slower performance and task constraints using matrix and loops
With these particular functions it's easy to precalculate the Jacobian function and do everything numerically (and quickly). Fo...

약 1달 전 | 0

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Local Stiffness Matrix Negative
How about replacing if i==2 & j==2 k=A(e)*E/(L/5); elseif i==2 & j==1 k=...

약 1달 전 | 0

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Save array values in a for loop
Try replacing error = max(abs(double(y1-z1(vx)))) with error(i) = max(abs(double(y1-z1(vx))));

약 2달 전 | 0

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Solving a PDE with two variables using cank nicolson method
Matlab indices start at 1, so the loops i, j and K in the following for i=0:N for j=0:M for K=0:1 f(x,y...

약 2달 전 | 0

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Solving a System of 2nd Order Nonlinear ODEs
You haven't passed y and z to the funcion in function dydt=mbd(M,m,g,lc,k) Probably needs to be more like function dydt=mbd(t...

약 2달 전 | 0

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Can I comment only a section or part of a line?
Like this: x = linspace(0,2*pi,100); y1 = sin(x); y2 = cos(x); plot(x,y1,... % comment x,y2)

약 2달 전 | 0

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In Matlab 2018 try title({'Main title text';'subtitle text'}) (Note the curly brackets)

2달 전 | 0

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Left-rotating a vector
You define B as a null vector so it doesn't have an "end". Try, simply A = [1,2,3,4,5]; B = [A(2:end) A(1)]

2달 전 | 0

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How can I solve this error : Invalid text character. Check for unsupported symbol, invisible character, or pasting of non-ASCII characters.
This works for me: n=input('donner le nombre de points: '); k=0; for i=1:n u1=rand;u2=rand; x=2*u1; y=2*u2...

2달 전 | 0

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Lax-Wendroff method for advection equation with periodic boundary condition
If you make dt=0.1*h/a; instead of dt=0.95*h/a; your max error reduces to 0.0355.

2달 전 | 0

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I want to solve the unknown variable t1
Well, this gets it working, though who knows if it makes any sense!" A0 =500; D0=100; c1=5; c2=10; c3=10; c4=8; a=30; a2...

2달 전 | 0

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How to make convergence plot (error VS time step) in a log-log scale among four numerical methods and exact solution?
This should give you the right idea: %% 1st-order Adams-Bashforh Solution fun = @(t,y) (y); %Function f(t,y) y0 = 1; %Initial...

3달 전 | 0

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i need some help with finding the damping ratio
Use fzero: x = [12.73, 25.36, 37.99]; y = [0.77, 0.29, 0.11]/2; zeta = fzero(@(zeta) fn(zeta,y),0.5); disp(['zeta = ' nu...

3달 전 | 0

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How to make graph that plot between Analytical Solution (Exact Solution) and Numerical Method Solution?
After Y = exactY(t2) you probably need something like: plot(t2,Y2,t2,Y) legend('AM','Exact') However, you haven't supplied th...

3달 전 | 0

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How to numerically solve and plot definite integral with variable upper limit
Like so: K= @(t) (sin(t)-t.*cos(t)).*sin(t); P = 0:0.1:3.1416; for i = 1:numel(P) V(i) = integral(K,0,P(i)); ...

3달 전 | 0

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