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# How can i fix ' Unable to perform assignment because the left and right sides have a different number of elements.' in the loop functions ?

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Kholoud S on 23 Jun 2019
Closed: MATLAB Answer Bot on 20 Aug 2021
I got errors in Rdot, alpha3, Rdot2
R2= 16;
R3=33;
omega2= 3;
i=0;
j=0;
for theta2= 0:5:180;
theta2=theta2*pi/180;
i=i+1;
x(i)=theta2;
%position
theta3 = pi - asin(R2*sin(theta2)/R3);
R1(i)= (R2*cos(theta2) - R3*cos(theta3));
%velocity
omega3 (i) = (omega2*R2*cos(theta2))/(R3*cos(theta3));
Rdot(i) = (-R2*omega2*sin(theta2))+ (R3*omega3*cos(theta3));
%acceleration
alpha3 (i) = ((-omega2.^2)*R2*sin(theta2)+ (omega3.^2)*R3*sin(theta3))/R3*cos(theta3);
Rdot2(i) = -R2*(omega2^2)*cos(theta2) + R3*alpha3*sin(theta3) + R3*(omega3^2)*cos(theta3)
theta33(i) = theta3*180/pi;
theta22(i) =theta2*180/pi;
end
per isakson on 23 Jun 2019
BTW, doc says: "Avoid assigning a value to the index variable within the loop statements."

infinity on 23 Jun 2019
Since "omega3" is a vector, which is not scalar and you calculate alpha3 by using omega3. So, I suggest you change "omge3" in
Rdot(i) = (-R2*omega2*sin(theta2))+ (R3*omega3*cos(theta3));
%acceleration
alpha3 (i) = ((-omega2.^2)*R2*sin(theta2)+ (omega3.^2)*R3*sin(theta3))/R3*cos(theta3);
by
omega3(i)
If this is not your formula, you should check it again.

per isakson on 23 Jun 2019
Edited: per isakson on 23 Jun 2019
One thing is to make a code run without throwing errors, another is to make it produce the intended result.
Replacing omega3 by omega3(i) and alpha3 by alpha3(i) in the right hand side of the lines, which throw errors, makes the code run.