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Alan Stevens


Last seen: Today
743 total contributions since 2020

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Answered
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...

environ 5 heures 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...

environ 6 heures ago | 1

Answered
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...

1 jour ago | 0

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

2 jours 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...

2 jours 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...

2 jours ago | 0

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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...

3 jours 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...

3 jours 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...

3 jours 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...

3 jours 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...

3 jours 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);

4 jours 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...

4 jours ago | 0

Answered
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...

4 jours ago | 0

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Answered
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...

4 jours 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 ...

4 jours 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; ...

4 jours ago | 0

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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...

5 jours 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...

5 jours ago | 1

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Boucle for add the element behind
doc cumsum

6 jours 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 ...

6 jours ago | 0

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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] ...

7 jours 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.

8 jours ago | 1

Answered
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 ...

8 jours 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...

8 jours ago | 1

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Answered
Solving second order inhomogeneous differential equations which are not a function of time
Break the ode into two first order ode's. e.g. dy/dx = v; dv/dx = f(x) - p*v - q*y; Look up the documentation on ode45 ...

8 jours ago | 0

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Answered
Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters
Your line v(n)= 4(-1)^(n-1)/(2(n-1)+1)+pi_estimate should be v(n)= 4*(-1)^(n-1)/(2*(n-1)+1)+pi_estimate Note: | ...

8 jours ago | 0

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How do I plotting Matlab functions, ode23, exact value functions side by side?
Like this format long r=5000; c=200*(10^(-6)); vs=10; tf=3; %%%%%%%%%%%%%%%%%%%%%%%%% %% 2 exact solution for charging an...

8 jours ago | 1

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Answered
Need to plot a graph of -y(t) and x(t) on MATLAB
Here are the equations that you will need to include in your pend function. Now let's see you implement them!

8 jours ago | 0

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