My for loop gives an error

alpha=sym('alpha',[1 6])
theta=sym('theta',[1 6])
d=sym('d',[1 6])
a=sym('a',[1 6])
A=sym('A',[1 6])
for S=[1 2 3 4 5 6]
A(S)=[cos(theta(S)),-sin(theta(S))*cos(alpha(S)),sin(theta(S))*sin(alpha(S)),a(S)*cos(theta(S))
    sin(theta(S)),cos(theta(S))*cos(alpha(S)),-cos(theta(S))*sin(alpha(S)),a(S)*sin(theta(S))
    0,sin(alpha(S)),cos(alpha(S)),d(S)
    0,0,0,1]
end

My answer is as follows

>> NEW

alpha =

[ alpha1, alpha2, alpha3, alpha4, alpha5, alpha6]

theta =

[ theta1, theta2, theta3, theta4, theta5, theta6]

d =

[ d1, d2, d3, d4, d5, d6]

a =

[ a1, a2, a3, a4, a5, a6]

A =

[ A1, A2, A3, A4, A5, A6]

In an assignment A(:) = B, the number of elements in A and B must be the same.

Error in sym/privsubsasgn (line 1067)

L_tilde2 = builtin('subsasgn',L_tilde,struct('type','()','subs',{varargin}),R_tilde);

Error in sym/subsasgn (line 904)

C = privsubsasgn(L,R,inds{:});

Error in NEW (line 7)

A(S)=[cos(theta(S)),-sin(theta(S))*cos(alpha(S)),sin(theta(S))*sin(alpha(S)),a(S)*cos(theta(S))

Answer 1

[Luna]

You can put your symbolic 4x4 matrices into a cell array.

Also your for loop is wrongly defined like for S = [1 2 3...]. You should define for S from 1 to 6.

alpha=sym('alpha',[1 6])
theta=sym('theta',[1 6])
d=sym('d',[1 6])
a=sym('a',[1 6])
% A=sym('A',[1 6])
A_new = cell(1,6); % preallocation of cell array
for S = 1:6
A_new{S} = [cos(theta(S)),-sin(theta(S))*cos(alpha(S)),sin(theta(S))*sin(alpha(S)),a(S)*cos(theta(S))
    sin(theta(S)),cos(theta(S))*cos(alpha(S)),-cos(theta(S))*sin(alpha(S)),a(S)*sin(theta(S))
    0,sin(alpha(S)),cos(alpha(S)),d(S)
    0,0,0,1]
end

So whenever you want to reach them individually you can type:

A_new{1} 

it gives the result for 1st 4x4 matrix as follows:

>> A_new{1}
ans =
[ cos(theta1), -cos(alpha1)*sin(theta1),  sin(alpha1)*sin(theta1), a1*cos(theta1)]
[ sin(theta1),  cos(alpha1)*cos(theta1), -sin(alpha1)*cos(theta1), a1*sin(theta1)]
[           0,              sin(alpha1),              cos(alpha1),             d1]
[           0,                        0,                        0,              1]

[Muhammad Waseem]

Thank you for the help, i didn't know how i would've pre-allocate a cell array i'll keep that in mind. During this and the next code

[Luna]

Your welcome :)