Unreconized function or variable

Unrecognized function or variable 'vR'.

Error in rectifier_code (line 60)

plot(t,vS,'--',t,vR)

I am starring at this program trying to understand why I cannot get it to run. Is it the for loop that is not defined properly that is causing the program not to define vR?

% Specify amplitude of source voltage
A = 1;
% Specify the frequency (in Hz) of the source voltage
f = 60;
% Specify the value of the capacitor (in micro-Farads)
CuF = 10;
% Specify the value of the capacitor (in Farads)
C = CuF*1e-6;
% Specify the value of the resistor (in Ohms)
R = 2000;  % 2 kilo-Ohm
% Specify a time-vector ranging from 0 to 70 milliseconds in increments of
% 0.1 milliseconds
t = 0:0.1e-3:70e-3;  %%% EXPRESSION FOR TIME VECTOR
% Specify the source voltage over all time
vS = A*sin(2*pi*f*t);

% The SWITCH variable is 'diode' and will take on character values of
% either 'on' or 'off'.  Initialize to 'on'.
diode = 'on';
% Loop over the time vector
for k = 1:length(t) %%% FOR-LOOP CODE WITH LOOP VARIABLE k
    % SET UP SWITCH STRUCTURE
    switch diode    %%% SWITCH CODE HERE
        % RUN THE CASE WHEN THE DIODE IS ON
        case 1   %%% CASE CODE HERE
            vR(k) = vS(k);  % resistor voltage is equal to source voltage
            iR(k) = vR(k)/R;  % i = v/R (Ohm's law)
            iC(k) = C * 2*pi*f * A*cos(2*pi*f*t(k));  % capacitor current
            iD(k) = iR(k) + iC(k); % current through the diode
            if iD(k) <= 0,
                diode = 'off';
                t_off = t(k);  % keep track of the time of diode turn-off
            end
            % RUN THE CASE WHEN THE DIODE IS OFF
        case 2  %%% CASE CODE HERE
            vR(k) = A*sin(2*pi*f*t_off) * exp(-(t(k) - t_off) / (R*C) );
            if vS(k) >= vR(k);
                diode = 'on';
            end
    end
end
% Plot the source and resistor voltages
plot(t,vS,'--',t,vR)

Unrecognized function or variable 'vR'.

axis([0 70e-3 -1.5 1.5])
legend('Source voltage','Resistor voltage')
title(strcat('Half-wave Diode Rectifier for C =',num2str(CuF),'\muF'))
ylabel('voltage (volts)')
xlabel('time (seconds)')

Answer 1

[Matt J]

vR is never defined because none of your switch cases are ever satisfied. One solution:

    switch diode    %%% SWITCH CODE HERE
        
        case 'on'  % RUN THE CASE WHEN THE DIODE IS ON

          ....
              
        case 'off'  % RUN THE CASE WHEN THE DIODE IS OFF
       

         ....
             
        otherwise
 
          error 'Unrecognized case';
          
    end

[Jason]

Wow... I knew it was simple. Thank you

[Matt J]

You're very welcome, but please Accept-click the answer to indicate that the question's been resolved.