hello I am getting this warning: Index in position 1 is invalid. Array indices must be positive integers or logical values. Error in dev4 (line 121)

close all

% Données

k1 = 50;
k2 = 500;
M_c = 864.4; % Mass of the cabin
n_b = 3; % Number of blade
M_b = 33.9 * n_b; % Mass of the blades
M_E = 100; % Mass of the engine
M_h = 20; % Mass of horizontal tailplane
M_bt = 14; % Mass of the tail rotor blades (as rigid body)
M_v = 15; % Mass of the vertical tailplane
x_D = 1.8;
x_G = 6;
x_F = 3;
x_C = 2.5;
h_c = 0.3049;
h_E = 0.85;
h_b = 1.7;
J_yc = 2113;
J_zb = 918 ;
J_yh = 6.7 ;
J_yt = 1.31 ;
J_yv = 8.5;
l = 6;
m = 9.82; % Masse par unité de longueur de la queue
I_y = 1.7521 * 10^(-5);
E = 7*10^(10);

freq = load('P2021_freqz');
modes = load('P2021_modes_z');

% Méthode de Rayleigh-Ritz

% On va construire les matrices M et K avec les formules de m_ij et k_ij

n = 22; % Nombre de fonctions d'essais w_i 
M = zeros(n);
K = zeros(n);

for j = 0 : n
    for i = 0 : n
        term1_m = (m*l^(i+j+1))/(l^(i+j)*(i+j+1));
        
        if (i == 1 && j == 1)
            term2_m = J_yc/l^2;
        else
            term2_m = 0;
        end
        
        if (i == 1 && j == 1)
            term3_m = M_c * x_c^2/l^2;
        else
            term3_m = 0;
        end
        
        if (i == 0.5 && j == 0.5)
            term4_m = M_c * x_c/2*l;
        else
            term4_m = 0;
        end
        
        if (i == 0.5 && j == 0.5)
            term5_m = M_c * x_c/2*l;
        else
            term5_m = 0;
        end
        
        if (i == 1 && j == 1)
            term6_m = M_c * h_c^2/l^2;
        else
            term6_m = 0;
        end
        if (i == 1 && j == 1)
            term7_m = M_c * h_E^2/l^2;
        else
            term7_m = 0;
        end
        
        if (i == 1 && j == 1)
            term8_m = J_yb /l^2;
        else
            term8_m = 0;
        end
        
        if (i == 1 && j == 1)
            term9_m = M_b * x_D^2/l^2;
        else
            term9_m = 0;
        end
        
        if (i == 0.5 && j == 0.5)
            term10_m = M_b * x_D/2*l;
        else
            term10_m = 0;
        end
        
        if (i == 0.5 && j == 0.5)
            term11_m = M_b * x_D/2*l;
        else
            term11_m = 0;
        end
        
        if (i == 1 && j == 1)
            term12_m = M_b * h_b^2/l^2;
        else
            term12_m = 0;
        end
        
        term13_m = M_h*(x_F/l)^(i+j);
        term14_m = J_yh*i*j*((x_F)^(i+j-2)/l^(i+j));
        term15_m = M_bt*(x_G/l)^(i+j);
        term16_m = J_yt*i*j*((x_G)^(i+j-2)/l^(i+j));
        term17_m = M_v*(x_G/l)^(i+j);
        term18_m = J_yv*i*j*((x_G)^(i+j-2)/l^(i+j));
        
        M(i,j) = term1_m + term2_m + term3_m + term4_m + term5_m + term6_m + term7_m + term8_m + term9_m + term10_m + term11_m + term11_m + term12_m + term13_m + term14_m + term15_m + term16_m + term17_m + term18_m;               
    end
end

for j = 0 : n
    for i = 0 : n
        if(i > 2 && j > 2)
            term1_k = E*I_y*i*j*(i-1)*(j-1)*(l^(i+j-3)) / ((l)^(i+j) * (i+j-3)) ;
        else
            term1_k = 0;
        end
        
        if (i == 1 && j == 1)
            term2_k = k1*x_D^2/l^2;
        else
            term2_k = 0;
        end
        
        if (i == 0.5 && j == 0.5)
            term3_k = k1 * x_D/2*l;
        else
            term3_k = 0;
        end
        
        if (i == 0.5 && j == 0.5)
            term4_k = k1 * x_D/2*l;
        else
            term4_k = 0;
        end
        
        if (i == 1 && j == 1)
            term5_k = k2/l^2;
        else
            term5_k = 0;
        end
        
        
        K(i,j) = term1_k + term2_k + term3_k + term4_k + term5_k;
    end
end

[Image Analyst]

You forgot to attach the .mat files.

freq = load('P2021_freqz');
modes = load('P2021_modes_z');

so I can't run your code. In the meantime, see the FAQ:

https://matlab.fandom.com/wiki/FAQ#.22Subscript_indices_must_either_be_real_positive_integers_or_logicals..22

Answer 1

[Voss]

Indexing in MATLAB starts at 1, not 0.

Your loops iterate starting with 0 and then try to use that as an index, hence the error.

[Cedrick De Block]

thank you very much, I forgot it😄😄