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Alan Stevens


Last seen: Today
748 total contributions since 2020

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Answered
Unable to perform assignment because the left and right sides have a different number of elements
Like this? % 1. Define Initial Conditions N = 50; % x_0 = 50*pi/180*randn(2,N); phi_0 = x_0(1,:...

19 hours ago | 0

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Answered
euler method for solving system of ODE's 1st order
Simple Euler inaccurate for large step size. Reduce step size as in following and see if you get the output you expect: a=0; %...

3 days ago | 1

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How to stop ODE(R4K) function when the value is close to 0?
Have you tried replacing u_p(i+1)=u_p(i)+h/6*(k1u_p+ 2*k2u_p + 2*k3u_p +k4u_p); with u_p(i+1)= max(u_p(i)+h/6*(k1u_p+ 2*k2u_p...

4 days ago | 0

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how can i solve this problem and plotting?
I assume you want to find the values of a that make the integral = 75, for all values of x. if so, then the following should do...

4 days ago | 1

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speeding up my for loop
Is this any quicker? function y = divisors1(N) i = 1:floor(N/2); L = lcm(N,i); y = sum(L==N) + 1; e...

4 days ago | 0

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Mark the knee point on a graph
Calculate a vector of values of P = V.*I then choose the maximum. Something like: P = V.*I; indx = find(P==max(P)); Vp = V(in...

5 days ago | 0

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Discretising a size distribution function and area under the curve
You should have log(sigma)^2, not log(sigma^2). Don't forget the "dx" part when integrating the curve. mu = 0.015; % geometri...

5 days ago | 1

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ODE system initial condition results in infinity/NaN error. Initial conditions cannot be changed. How to evade?
Simply write your differential function as: fu_p = @(D_p,u_p) -18*muG*u_p/(rhoP*D_p^2) + g*(rhoP-rhoG)/rhoP; avoiding any expl...

5 days ago | 0

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Single bubble expansion equation
Try starting your bubble radius as 2*sigma/1.4, rather than 0.

6 days ago | 0

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Coupled rate ODEs with ode45
It can all be done in one script as follows. Because of the orders of magntude difference between the various concentrations th...

7 days ago | 0

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How can I call the highest order solution (e.g. x'') of an ode in another ode?
You can rearrange the equations as follows to get a consistent set: (you will need to use explicit multiplication where my eq...

7 days ago | 0

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Answered
How can I make a loop that gives values in each iteration?
Why do you need a loop? There is just one zero between 2 and 8. Your values of w are not used in any meaningful way (they woul...

7 days ago | 0

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How to use ODE 45 to generate a SIR model
Like so: alpha=1.99; beta=1; gamma=1/7; S=0.99; I=0.01; R=0.1; %tstart=0; %tend=100; y=[S,I,R]; tspan=0:1:100; [t,sol...

8 days ago | 2

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error in using the function fsolve to find steady state
Using the Optimization toolbox to solve these equations seems like using a sledgehammer to crack a nut! It is clear from the eq...

8 days ago | 0

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I am trying to solve ODE having more than 1 dependent variable. but I am not able to solve it with dsolve function. please help me to find correct function to solve ODE.This is an mechanical engineering equation so it is bit complicated and lengthy
Here's a possible way using ode45. I've used arbitrary initial values for the three temperatures, so you will need to replace t...

8 days ago | 1

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Answered
MATLAB Newton Raphson Method with a function with array/matrix variables
You could do it like this f = @(x,g) g.*exp(x) - 1; df = @(x,g) g.*exp(x); g = [1 2 3 4 5]; for i= 1:numel(g) x0 = 0...

8 days ago | 1

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Answered
When i try to create function error "Unable to perform assignment because the left and right sides have a different number of elements." comes up
Try n=-25:25; x3=zeros(1,length(n)); x3(n>=2 & n<=22)=exp(j*(0.5)).^(2:22);

8 days ago | 0

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Answered
Explicit Eulers Method for time advancement
T(i)^(n+1) This will raise T(i) to the (n+1)th power! You need another loop for time (say j = 1:something), then you can refer...

8 days ago | 0

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Hot to fit two curves under interdependent constraint ?
How about just using fminsearch x = linspace(1,100,100); % Measurement results: y1=[0.07469056,0.07378624,0.07288704,0.071992...

9 days ago | 0

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Need assistance using bisection method to find equation roots in Matlab function.
Try this % input for function that we're finding the roots of f1 = @(x) ((-0.6)*x^2)+(2.4*x)+(5.5); xl = 5; % xl sets the i...

9 days ago | 0

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Answered
Errors in Newton Raphson Code
Again, more like this % f = 3*exp(x)-4*cos(x) % df/dx = 3*exp(x)+4*sin(x) i=1; x=0.1; err = 1; while err>10^-8 && i<100 ...

9 days ago | 0

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Error in Newton-Raphson Method
Like this R=15/2; v=500; h=8; i=1; err = 1; while err>10^-8 && i<100 hold = h; fh = pi*h^2*(3*R - h)/3 - v; ...

9 days ago | 0

Answered
Plotting partial sums of series
Do you mean something like this? x = -pi:0.1:pi ; %initializing x S = zeros(20,numel(x)); figure xlim([1 20]) grid hold o...

9 days ago | 0

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Answered
Anonymous function surface plot
Are you looking for something like this? n = 2; x_opt = randi([-6,6],n,1); A = randi(n,n); T = A*A' + eye(n,n); h = -T*x_op...

10 days ago | 1

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Answered
Boucle for add the element behind
doc cumsum

10 days ago | 1

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Solving system of ODEs and Plotting
Something like this? timerange= [0 60]; [t, hvl] = ode45(@f, timerange, [0.9,0.1,0.2]); plot(t, hvl, 'LineWidth', 2),grid ...

11 days ago | 0

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Answered
Plot 3D of a function
Are you looking for something like this? x = linspace(0,pi); t = linspace(0,1); z = @(x,t) 10*exp(-4*t).*sin(2*x); [x1, t1] ...

12 days ago | 0

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Answered
Error using _*_. What am I doing wrong?
You need dots before the * and before the / , not after the t.

12 days ago | 1

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Runge Kutta 4th Order Example
First, write your equation as two first order equations; xdot = v, say, and vdot = -9xdot - 0.1x^3 Then define two functions ...

12 days ago | 1

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Find intersection point between a vertical line and another line.
You could insert a conditional: AlineX=[0 0]; AlineY=[0 400]; BLineX=[1180 570]; BLineY=[-289.5 250]; p1 = polyfit(Alin...

12 days ago | 1

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