P(t)=25sin(35t) euler method

Question

Fernando Piedra 2020-11-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/645183-p-t-25sin-35t-euler-method

回答： Jon 2023-6-19

%i need help with my getder file which take the derivative of the funtion.
%there are 3 file main where define all variables getder which i obtain the derivative
%and box_solve to solve and create a plot using eulers or RK method.
%Many thanks in advance
%main file 
v0 = 0;
s0 = 0;
m = .5;
k = 75;
%getder file to obtain a the derivative
function xdot = getder(t,x)
x = [s;v];
a = (1/m)*(25*sin(45*t)-k*so);
xdot = [s;a];
%box_solve file to solve equation through euler method or Rk.
function [t,x] = box solve(x0,tlim,dt,solve_type)
if st == 1 %solve type allow operator to 
    t = (to:dt:tf).'
    L = length(t);
    x = xeros([l,2])
    x(1,:) = xo.'
    for n =1:L
        x(n+1,:) = x(n,:)+dt*geter(t(n),x(n,:));

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MANIK 2023-6-19

Hi @Fernando Piedra,

Can you be please more clear regarding your doubt in the code?

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Answer 1

Jon 2023-6-19

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/645183-p-t-25sin-35t-euler-method#answer_1258789

在 MATLAB Online 中打开

Just glancing at your code I can see a number of errors:

The variable s is not defined anywhere before you call this line of code in getder

x = [s;v];

So, MATLAB will not know how to make that assignment since it doesn't know what s is.

In the next line of code

a = (1/m)*(25*sin(45*t)-k*so);

It looks like you have a variable called so (also not defined) you probably meant s0 (that's the number zero as the second character rather than the letter o)

In this line you do not use a valid name for the function. You can not have spaces in a function name.

function [t,x] = box solve(x0,tlim,dt,solve_type)

You probably have even more errors but that should at least get you started