Plotting damped sine travelling wave equation in Matlab

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Jesse
Jesse 2015-2-20
回答： Jesse 2020-4-24
Greetings all,
Please correct me if I am wrong on any of this, but I am trying to plot a damped/attenuating sine wave of the form y(x,t)=Ae^-alpha(x) * sin(wt-Bx + phi).
Granted the sin is not in the exponential, I've been trying to code this up knowing that travelling waves have spatial as well as temporal dimensions.
The code I have after user input is:
x=0:.001:1;
Beta = 2*pi/lambda; %(lambda is user input)
y1=zeros(100,100);
for t=0:.001:1
y1(t,:)=A*sin(Beta*x-w*t + phi).exp(-alpha*x)
end
%A, alpha, w, and phi are user input as well
So I'm getting a "Subscript indices must be either real positive integers or logicals." Where am I going wrong?
Also, I am trying to plot this damped wave - do I need to use plot3? If so, why?
Thanks!
-J
  1 个评论
Prasad Reddy
Prasad Reddy 2020-4-24
y1(t,:)=A*sinBeta.*x-w*t+phi).*exp(-alpha.*x)
please check the above equation. it may work.
you need not to use plot3 command.

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采纳的回答

KSSV
KSSV 2020-4-24
编辑：KSSV 2020-4-24
You index t, is taking zero for the first time. Indices cannot be negative and zero in MATLAB. You need not to use loop, you can follow as below.
clc; clear al ;
A = rand ;
lambda = rand ;
w = rand ;
phi = rand ;
alpha = rand ;
x=0:.001:1;
Beta = 2*pi/lambda; %(lambda is user input)
t=0:.001:1 ;
[X,T] = meshgrid(x,t) ;
Y1 = A*sin(Beta*X-w*T + phi).*exp(-alpha*X) ;
surf(X,T,Y1)

更多回答（2 个）

Deepak Gupta
Deepak Gupta 2020-4-24
Your y1 seems to be function of two variables x and t so yes, you will need to use plot3 at it will plot y1 against two variables.
You can try below code to find value of y1:
x=0:.001:1;
t =(0:.001:1)';
Beta = 2*pi/lambda; %(lambda is user input)
y1=zeros(1001,1001); % y1 should have same dimention as x*t matrix.
y1=A*sin(Beta*x-w*t + phi).*exp(-alpha*x)
plot3(t, x, y1)
Jesse
Jesse 2020-4-24
Thanks all but this question was posted 5 years ago, and I think it had to do with some project I was working on at the time.
Thank you again for the responses and your time.

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