Alan Stevens
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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,:...
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
| accepted
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; %...
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
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...
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
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...
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
| accepted
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...
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
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...
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
| accepted
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...
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
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...
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
| accepted
Answered
Single bubble expansion equation
Try starting your bubble radius as 2*sigma/1.4, rather than 0.
Single bubble expansion equation
Try starting your bubble radius as 2*sigma/1.4, rather than 0.
6 days ago | 0
| accepted
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...
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
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...
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
| accepted
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...
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
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...
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
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...
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
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...
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
| accepted
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...
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
| accepted
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);
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
| accepted
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...
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
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...
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
| accepted
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...
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
| accepted
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 ...
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
Answered
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; ...
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...
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
| accepted
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...
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
| accepted
Answered
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 ...
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
| accepted
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] ...
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
| accepted
Answered
Error using _*_. What am I doing wrong?
You need dots before the * and before the / , not after the t.
Error using _*_. What am I doing wrong?
You need dots before the * and before the / , not after the t.
12 days 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 ...
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
Answered
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...
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
| accepted
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