Left and Right side have different elements

For theta_dot(i) specifically, I keep running into the error "Unable to perform assignment because the left and right sides have a different number of elements". I'm amateur with MatLab and need help fixing that line.

t = 0:0.01:4; % Timesteps for robotic arm motion

for i = 1:length(t)

% Position of robotic arm in r-theta coordinates

theta(i) = -(pi/4)*t.^2+pi*t;

r(i) = 3+0.5*cos(4*theta(i));

% Position of robotic arm in x-y coordinates

x(i) = r(i)*cos(theta(i));

y(i) = r(i)*sin(theta(i));

% Velocity of robotic arm in radial/transverse components

theta_dot(i) = -(pi/2)*t+pi;

r_dot(i) = pi*sin(4*theta(i));

v_r(i) = r_dot(i);

v_theta(i) = (r(i)*theta_dot(i));

% Velocity of robotic arm in Cartesian coordinates

% v_x(i) = MODIFY;

% v_y(i) = MODIFY;

Answer 1

[Star Strider]

You need to subscript ‘t’.

Then, it works —

t = 0:0.01:4;            % Timesteps for robotic arm motion
for i = 1:length(t)
    % Position of robotic arm in r-theta coordinates
    theta(i) = -(pi/4)*t(i).^2+pi*t(i);                                 % <— Changed: 't' To 't(i)'
    r(i) = 3+0.5*cos(4*theta(i));
    % Position of robotic arm in x-y coordinates
    x(i) = r(i)*cos(theta(i));
    y(i) = r(i)*sin(theta(i));
    % Velocity of robotic arm in radial/transverse components
    theta_dot(i) = -(pi/2)*t(i)+pi;                                     % <— Changed: 't' To 't(i)'
    r_dot(i) = pi*sin(4*theta(i));
    v_r(i) = r_dot(i);
    v_theta(i) = (r(i)*theta_dot(i));
    % Velocity of robotic arm in Cartesian coordinates
    % v_x(i) = MODIFY;
    % v_y(i) = MODIFY;
end

v_theta

v_theta = 1x401

10.9956 10.9283 10.8372 10.7236 10.5890 10.4352 10.2645 10.0790 9.8812 9.6737 9.4590 9.2398 9.0186 8.7979 8.5801 8.3676 8.1625 7.9667 7.7820 7.6099 7.4517 7.3085 7.1812 7.0702 6.9760 6.8986 6.8381 6.7940 6.7659 6.7532

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figure
plot(t, v_theta)
grid
xlabel('t')
ylabel('v\_theta')

.

Answer 2

[Torsten]

Replace t by t(i) in the loop.