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Alan Stevens


Last seen: Today
760 total contributions since 2020

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Answered
How to control the outcome of an ODE?
How about just modifying dydt(5) within the function to % Temperature if y(5)>=600 dydt(5) = 0; else dydt(5) = ( (...

alrededor de 19 horas ago | 0

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Answered
Error when solving differential equations
Your function has function dydt = vdpi1(t,y) but you really want dy returned, not dydt.

1 día ago | 0

Answered
not getting plot , why?
Arrange it like this sigma=0.047193; V_tip=180; W=180; Cd_avg=0.01; R=2.235; k=1.1; A=pi*R.^2; P_e= 61147.4; h=0:100:...

1 día ago | 0

Answered
Solving a linear system of 1st order ODEs using the Forward Euler method and ode45
You were confusing time and x position. Try tf = 4; %final time You are integrating wrt time not x tspan = [0,tf]; h = .05;...

1 día ago | 0

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Answered
How can I solve this ode problem?
You get a singularity (divide by zero) when u = 60, giving infinite acceleration. You need to include a guard against this.

2 días ago | 1

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Answered
My function f(x) doesn't display (compute?) the result for when f = 0.
Replace diff(g) by gradient(g)

4 días ago | 1

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Taking a descend interval
Insert tau = n+1-t; then raise 1/800 to the power tau.

4 días ago | 0

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Answered
Complex Sinwave to plot
Like this x = 0:0.1:4.56; p = zeros(1,numel(x)); q = zeros(1,numel(x)); for i = 1:numel(x) p(i) = fn(x(i)); q(i) =...

5 días ago | 0

Answered
Extreme difference between the value of a function and the result in matlab
Must hit an overflow. Express it as: a=sqrt(4950000001); b=30000; r = (a/b)^2; y1 = 333.75+r*(11*r - b^2 -121 - 2/b^4)+5.5*...

5 días ago | 1

Answered
How to calculate the projection of point onto a line
Try doc std

6 días ago | 0

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,:...

7 días 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; %...

9 días ago | 1

Answered
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...

10 días ago | 0

Answered
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...

10 días ago | 1

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Answered
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...

10 días ago | 0

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...

11 días ago | 0

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Answered
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...

11 días 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...

12 días ago | 0

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

13 días ago | 0

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Answered
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...

13 días ago | 0

Answered
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...

13 días 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...

13 días ago | 0

Answered
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...

14 días ago | 2

Answered
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...

14 días ago | 0

Answered
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...

14 días 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...

14 días 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);

14 días 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...

15 días ago | 0

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