error: elobrate on it

% Optimization of Tuned mass damper parameters
wn = input('natural frequency of main system, wn:');
z = input('damping factor,z:');
ms = input('mass of main system, ms:');
md = input('mass of damper system, md:');
%  Tuned damper parameters
kd = input('Stiffness of damper, kd:');
zd = input('damping factor, zd:');
wd = kd/md;
w = 0:1:1000;
%  Non-dimensional parameters
r = w/wn;
rd = wd/wn;
m = ms/md; %  Fixed for a setup
 for s=1: length(r)
G(s,:)= sqrt((rd.^2-r.^2).^2+4*zd.^2*rd.^2*r.^2)./{((1-r.^2)*(rd.^2-r.^2)-m*rd.^2*r.^2-4*z*zd*rd*r.^2).^2+4*(zd*rd*r*(1-r.^2-m*r.^2)+z*r*(rd.^2-r.^2)).^2}.^(1/2);
Re(s,:) = {(rd.^2 -r.^2)*(1-r.^2)*(rd.^2-r.^2)-m*rd.^2*r.^2+ 4*(zd.^2*rd.^2*r.^2*(1-r.^2-m*r.^2))}./{((1-r.^2)*(rd.^2-r.^2)-m*rd.^2*r.^2-4*z*zd*rd*r.^2).^2+4*(zd*rd*r*(1-r.^2-m*r.^2)+z*r*(rd.^2-r.^2)).^2}.^(1/2);
end
figure (1)
plot(r,G)
xlabel ('\omega/\omega_n')
ylabel ('|x (i\omega)|/F')
grid
figure (2)
plot(r, Re)
xlabel ('\omega/\omega_n')
ylabel ('Non-dimensional real part (Re)')
grid

error: 
Error using  * 
Inner matrix dimensions must agree.

Error in two_dof (line 16)G(s,:)  = sqrt((rd.^2-r.^2).^2+4*zd.^2*rd.^2*r.^2)./{((1-r.^2)*(rd.^2-r.^2)-m*rd.^2*r.^2-4*z*zd*rd*r.^2).^2+4*(zd*rd*r*(1-r.^2-m*r.^2)+z*r*(rd.^2-r.^2)).^2}.^(1/2);

Answer 1

[Walter Roberson]

The "*" operator is matrix multiplication.

Your variable "r" is a row vector, so (1-r.^2) is a row vector and (rd.^2-r.^2) is a row vector of the same length. You cannot matrix-multiply a 1 x N array by a 1 x N array: matrix multiplication requires that the second dimension of the first array be the same as the first dimension of the second array.

If your code gets past that, then your code will still fail, as you cannot apply arithmetic operations such as division to cell arrays. The {} brackets are only for building cell arrays. The [] brackets are only for building vectors and matrices. The () brackets are the only arithmetic grouping operators in MATLAB.

[Meyyappan]

Walter thankz for ur kind info. I have ended up in correcting the mistakes.