# Looking to plot yaw motion of an aircraft but get "Array indices must be positive integers or logical values." Error

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David Scidmore on 29 Jan 2021
Commented: VBBV on 29 Jan 2021
clear all
clc
N_phidot = -0.36752;
N_phi = -8.3569;
N_delta_r = -3.8313;
delta_R = -10;
sigma = 1/2.*N_phi;
omega_d = (-N_phi-1/4.*(-N_phidot)^2)^(1/2);
xi = 1/2.*(-N_phidot/-N_phi^(1/2));
omega_n = (-N_phi)^(1/2);
beta = (N_delta_r/N_phi).*delta_R;
phi = atan(sigma/omega_d);
alpha = -1/2.*beta.*(omega_n/omega_d);
Tau = 2*3.14/omega_d;
xiomega_n = 1/Tau;
t = [0:0.01:10];
Phi(t) = beta.*(1-(omega_n/omega_d.*exp(-sigma.*t).*cos((omega_d.*t)-phi)));
Phidot(t) = diff(Phi(t));
figure(1)
plot(t,phidot)
title('Phidot vs time')
xlabel('seconds')
ylabel('degrees')
figure(2)
plot(t, phi)
title('Phi vs time')
xlabel('seconds')
ylabel('degrees')
Error Messages
Array indices must be positive integers or logical values.
Error in HW1MAE503Q2 (line 22)
Phi(t) = beta.*(1-(omega_n/omega_d.*exp(-sigma.*t).*cos((omega_d.*t)-phi)));
>>

VBBV on 29 Jan 2021
%true
Phi = beta.*(1-(omega_n/omega_d.*exp(-sigma.*t).*cos((omega_d.*t)-phi)))
##### 2 CommentsShowHide 1 older comment
VBBV on 29 Jan 2021
Note that t is vector with decimal increments