Trying to code a state space modelling for thrust vector control of a rocket. I keep getting Error using plot, Invalid Data Argument, please help

%% STATE SPACE MODELLING %%1%
 
clc;
close all; 
clear all;
%-cosntant values
Iyy=2.186e8;
m=38901; 
Tc=2.361e6;
v= 1347; 
Cn_alpha=0.1465; 
g= 26.10;
N_alpha=686819; 
M_alpha=0.3807; 
M_delta=0.5726;
x_cg=53.19;
x_cp=121.2;
F=Tc;
 
%Othr important constants
Mach=1.4 %mach
h=34000; %height of the launch 
S=116.2,7 %Area of the platform 
Fbase=1000; %base drag
Ca=2.4; %coefficients 
D=Ca*680*3-Fbase; %-drag 
Drag=7.15*D %total drag	

%state space matrix
A_m=[0 1 0;M_alpha 0 M_alpha/v;-(F-Drag+N_alpha)/m 0 -N_alpha/(m*v)];
B_m=[0;M_delta;Tc/m];
C_m=diag([1 1 1])
D_m=[0; 0; 0]
pitch_ss= ss(A_m, B_m,C_m, D_m);

%%% COST FUNCTION %%% 

%cost function
 
cvector={'bo' 'ro' 'go'};
R_vector=[ 0.1 5 10]
%lowest weight to TVC angle, max to drift

figure;hold on;

for k=1:1
    R_matrix_drift=R_vector(k);
    Q_matrix_drift=[1 0 1/v; 0 0 0;1/v 0 1/v^2];
    [K S e] = lqr(pitch_ss,Q_matrix_drift,R_matrix_drift);
    for i=1:10000
        e_val( :,i ) =eig (A_m-B_m*K*i/10000);
    end
    plot(real(e_val(1,:)),imag(e_val(1,:)),cvector(k));
    plot(real(e_val(2,:)),imag(e_val(2,:)),cvector(k));
    plot(real(eval(3,:)),imag(e_val(3,:)),cvector(k));
    grid;
end
xlim([-2 1]);
legend ('R=0.1') ;
%LQR Gains are obtained
K_1=K(1); 
K_2=K(2); 
K_3=K(3);

Answer 1

[Walter Roberson]

cvector{k} not (k). You cannot pass a cell array into plot, you have to dereference it

[P.V. PRANAV]

Yet no result, the code is running but I do not see a plot?

Answer 2

[Sam Chak]

@Chinmay Kundapur, alternatively, you can directly write the color code straightaway.

Iyy      = 2.186e8;
m        = 38901; 
Tc       = 2.361e6;
v        = 1347; 
Cn_alpha = 0.1465; 
g        = 26.10;
N_alpha  = 686819; 
M_alpha  = 0.3807; 
M_delta  = 0.5726;
x_cg     = 53.19;
x_cp     = 121.2;
F        = Tc;
 
% Oth(e)r important constants
Mach  = 1.4; %mach
h     = 34000; %height of the launch 
S     = 116.27; %Area of the platform 
Fbase = 1000; %base drag
Ca    = 2.4; %coefficients 
D     = Ca*680*3-Fbase; %-drag 
Drag  = 7.15*D; %total drag	

% state space matrix
A_m      = [0 1 0; M_alpha 0 M_alpha/v; -(F-Drag+N_alpha)/m 0 -N_alpha/(m*v)];
B_m      = [0; M_delta; Tc/m];
C_m      = diag([1 1 1]);
D_m      = [0; 0; 0];
pitch_ss = ss(A_m, B_m, C_m, D_m)

pitch_ss =
 
  A = 
              x1         x2         x3
   x1          0          1          0
   x2     0.3807          0  0.0002826
   x3     -77.63          0   -0.01311
 
  B = 
           u1
   x1       0
   x2  0.5726
   x3   60.69
 
  C = 
       x1  x2  x3
   y1   1   0   0
   y2   0   1   0
   y3   0   0   1
 
  D = 
       u1
   y1   0
   y2   0
   y3   0
 
Continuous-time state-space model.

R_vector = [0.1 5 10];

% lowest weight to TVC angle, max to drift
figure; hold on;
for k = 1:1
    R_matrix_drift = R_vector(k);
    Q_matrix_drift = [1 0 1/v; 0 0 0; 1/v 0 1/v^2];
    [K S e]        = lqr(pitch_ss, Q_matrix_drift, R_matrix_drift);
    for i = 1:10000
        e_val( :,i ) = eig (A_m-B_m*K*i/10000);
    end
    plot(real(e_val(1,:)),imag(e_val(1,:)), 'bo');
    plot(real(e_val(2,:)),imag(e_val(2,:)), 'ro');
    plot(real(e_val(3,:)),imag(e_val(3,:)), 'go');
    grid;
end
xlim([-2 1]);
legend ('R=0.1');

%LQR Gains are obtained
K_1 = K(1)

K_1 = 3.9108

K_2 = K(2)

K_2 = 3.7074

K_3 = K(3)

K_3 = 4.5886e-04