why am i getting the error "Incorrect number or types of inputs or outputs for function step."

My code:

Kp5 = 10.1;
num5 = [2*Kp5];
den5 = [0.4 4.1 (1+2*Kp5)];
Ki6 = 0.0611;
num6 = 2*Ki6;
den6 = [0.4 4.1 1 2*Ki6];
Kp7 = 9.97;
num7 = 2*Kp7*[1 0.3];
den7 = [0.4 4.1 (1+2*Kp7) 0.6*Kp7];
figure; 
step(num5,den5);
hold on;
step(num6,den6);
step(num7,den7);
grid on;

Answer 1

[Walter Roberson]

The most likely problem is if you do not have Control System Toolbox installed.

Answer 2

[Paul]

Hi Salim

Your code runs fine here. What version of Matlab are you using?

I just changed the code to make separate plots intead of overlaying them all on one plot

Kp5 = 10.1;
num5 = [2*Kp5];
den5 = [0.4 4.1 (1+2*Kp5)];
Ki6 = 0.0611;
num6 = 2*Ki6;
den6 = [0.4 4.1 1 2*Ki6];
Kp7 = 9.97;
num7 = 2*Kp7*[1 0.3];
den7 = [0.4 4.1 (1+2*Kp7) 0.6*Kp7];
figure; 
step(num5,den5);

%hold on;
figure
step(num6,den6);

figure
step(num7,den7);

%grid on;

Having said that, those calls to step are using obsolete functionality. Instead use tf, ss, or zpk objects, like this

figure
step(tf(num5,den5))