plotting graph including sigma

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Sojung Park
Sojung Park 2023-3-12
评论： Sojung Park 2023-3-15
I am trying to plot this equation.
I have the values of B, omega_d, zeta, N_k and t_j is the multiples of 1.89.
Below is what I tried but the plot is weird and I can't find what's wrong.
Any comment will be helpfull. Thanks!
B_n=-5.36 ;
omega_d= 400;
zeta=29 ;
N_k=10;
sum=0;
for i=1:N_k
t_j= 1.89.*i;
sum= sum+ exp(-(zeta/2).*(t-t_j)).*(-zeta*(sin(omega_d/2.*(t-t_j)))+ omega_d.*cos(omega_d/2*(t-t_j)));
end
sum=B_n/omega_d.*sum;
t=0:10;
plot(t,sum)
  2 个评论
Walter Roberson
Walter Roberson 2023-3-12
We recommend against using sum as the name of a variable, as it is very common to find that in the same code one also needs to use sum as the name of a function.

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采纳的回答

Walter Roberson
Walter Roberson 2023-3-12
Ran in:
Your total is pretty large at small times, and by comparison decays to nothing. This behaviour continues, with large oscillations that dampen quickly relative to earlier values
syms t
Q = @(v) sym(v);
B_n = Q(-536)/100;
omega_d = Q(400);
zeta = Q(29);
N_k = 10;
parts = zeros(1, N_k, 'sym');
for i=1:N_k
t_j= 1.89.*i;
parts(i) = exp(-(zeta/2).*(t-t_j)).*(-zeta*(sin(omega_d/2.*(t-t_j)))+ omega_d.*cos(omega_d/2*(t-t_j)));
end
total = B_n/omega_d.*sum(parts);
fplot(total, [0 2])
fplot(total, [8 10])
  1 个评论
Sojung Park
Sojung Park 2023-3-15
Thank you so much!
I have an extra question. How can I change this code if there is a relation between N_k, t, t_j. The relation is that N_k is the integer of t/tt.(when I define t_j=tt*N_k)
I'm confused how I can get the each value when t is changing within the range and apply the effects on the other components.(I tried 'while' and 'if' but I got a warning messege 'Operands to the logical and (&&) and or (||) operators must be convertible to logical scalar values.')

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