Community Profile # Alan Stevens

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Mod Euler Method with two ODEs
Like this %Mod_Euler_method Modified Euler's method % [t, w, h] = euler_method(f, a, b, alpha, n) performs Modified Euler's me...

ein Tag ago | 0

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im having trouble finding the right values for this codes
This should allow you to find the right values, though it might not be quite the way you were tasked to do it! %Initial Conditi...

ein Tag ago | 0

Break the for loop
Something like this perhaps: fib = [1; 1]; its = 0; keepgoing = true; while keepgoing its = its+1; r = rand; ...

2 Tage ago | 0

How to take data on a column matrix (2661 x 1 double) for every 4 row then 3, sequently? So we take data only row 1, 5, 8, 12, 15, 19, 22, ... etc? Thank you.
Here's one way. There's probably a neater way. data=rand(1,2661); n = ceil(2661/3.5); ptr(1)=1; for i = 2:n ptr(i) = 4*(...

2 Tage ago | 0

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Random draws from conditional multinomial distribution
Something like u = rand(1) if u<0.2 d = 0; elseif u<0.7 d = 2571; elseif u<0.9 d = 2571^2; else d = 25...

2 Tage ago | 0

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How to define and plot a function with input range?
Like so: pt = @(t) (1 ./ (1 + t .^ 2)).*(t>=-0.5).*(t<=0.5); x = 0:0.01:10; y = 2*pt(x-1) + 4*pt(x-2) + 3*pt(x-3) + pt(x-4); ...

4 Tage ago | 0

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Plot the slope of a parabola with only the data points being known
Like this? x = linspace(-0.5,0.5,25); %length in (meters) def_3mm_no_grav = -[0.00 5.82e-1 1.08 1.53 1.94 2.30 2.62 2.89 3.12 ...

4 Tage ago | 1

SIRE with vaccine model
Like this tspan = [0 1.5]; options = odeset('Refine', 10, 'RelTol', 1e-4); y0 = [5185000*0.3 5185000*0.7 1 1 0 0 0 0]; [t,...

4 Tage ago | 1

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Problem with fplot function - displays grey zone instead of functions
Change all the ^ to .^ (i.e. dot^)and the * to .*

5 Tage ago | 1

I would like to create a handle function by for loop in matlab, but it does not work. I will be thankful if some body help me.
More like this? sfn = @(x,a,b) (a - b)*x; a=[1 2 3]; b=[4 5 6]; n=length(a); x = 1; % specify whatever x value you want f...

5 Tage ago | 0

How to solve this implicit equation in matlab?
Good idea to plot a graph first, to see roughly where the root lies. Then use fzero. For example:: fn = @(x)log((0.77*x-0.77)...

6 Tage ago | 0

Problem with solving discrete element method using leap frog method
The following gets the code working, but I've no idea if the results are meaningful!! n_part=4; kn=5; kt=2/7*kn; m=0.3; g=9...

7 Tage ago | 0

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Write a loop to plot a model graph
A little more like this. You need a smaller value of dv and a while loop. The fit isn't very good! %% Observed Wave dispersi...

7 Tage ago | 0

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Making a line thought points plotted from for loop in MATLAB
Like this? R1= 1399.580e+6; C1= 374.868e-6; R2= 1497.005e+6; C2= 350.472e-6; R3= 19573.407e+6; C3= 2429.373e-12;...

8 Tage ago | 0

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How do I plot and return the values of multiple intersections between a function and zero?
Here's one possibility (though you get repeated results for the roots!): det_a = @(x) sin(x).*cosh(x) - cos(x).*sinh(x); x=0:1...

8 Tage ago | 0

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Simplify Matrix decimal to integers
One way is M = [881/2158 985/1393 780/1351 881/2158 -985/1393 780/1351 -881/1079 ...

9 Tage ago | 0

Tring to solve for a transcendental equation
You can rearrange the equation as eigen*tan(eigen) = Bi and use fzero as below. However, because of the nature of tan, your res...

11 Tage ago | 0

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Question regarding MATLAB code to solve for electron in constant electric and magnetic field
If you are going to use global variables they need to be declared outside the function as well as inside. Your values of q and ...

14 Tage ago | 0

Hello, I am trying to plot the transmission coefficient vs energy for the double barrier potential, but I get an error. May I know what I have done wrong here?
See the following V_0 = 0.2800; % Barrier strength in eV hbar = 1.054571596e-34; % Reduced Planck constant m = 5.465629128e-3...

14 Tage ago | 0

Simulation of point kinetics reactor equations
There are seven equations if you are using all six delayed neutron groups. You don't give your reactivity, nor the individual b...

21 Tage ago | 0

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calculating angle between line of best fit and x axis
Take the arctangent of the gradient of the straight line.

21 Tage ago | 0

deleting separate zeros from vector
Here's one way (there is probably a slicker way!): A = [ 0 0 1 0 0 0 1 0 1 0 0 1 5 9 8 2 0 3 0 1 0 0 0 ]; ...

22 Tage ago | 0

Making a Euler Method script to solve for velocity but am encountering "Array indices must be positive integers or logical values" Error
Try changing your loop to for i=1:numel(t) %%% i loop not t f = (g - (D * p * A * v(i).^2)/(2*m)); %%% v(i) v(i+1) ...

22 Tage ago | 0

Error solving for a particular variable from two equations
You could use fzero: TonTc = 0.01:0.01:0.99; a = zeros(1,numel(TonTc)); a0 = 1; % initial giuess for k = 1:numel(a) ...

23 Tage ago | 0

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Replacing sym with function handle
Do you mean something like this? phi = pi/3; [nr, wr] = fn(phi); disp(phi) disp(nr(4)+56*3/2) disp(wr(4)) function [nr...

23 Tage ago | 0

I'm trying to solve this system of ODE's describing a mechanical spring model.
Might be better to forget about symbolics, treat each 2nd order ode as two first order ode's and do the following: %applied for...

26 Tage ago | 0

Solving a first order ODE with Euler backwards method
Your y_true is only valid for t>= 5 (smaller values give imaginary results for y). So, try going from 5 to 8: % y_true = log(t...

26 Tage ago | 0

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Need help to create a loop
How about: e=2.7183; gamma=0.1333; k = [1,9,23,7,23,9,20,29,63,102,73,59,27,130,75,185,70,92,326]; Rt=0:0.01:10; P = zero...

26 Tage ago | 1