Undefined function 'iosize' for input arguments of type 'double'.

Hello,

first time using Matlab.

I'm using MATLAB R2019a - academic use.

First of all I need to know if matlab files should be saved in a specific directory to be run correctly.

Then the main problem is that I wrote this simple script:

clear all
close all
clc

s = tf('s');
F = (s+10)/(s^3+45*s^2-250^s)

and then, errors appeared:

Undefined function 'iosize' for input arguments of type 'double'.

Error in  ^  (line 26)
[ny,nu] = iosize(M);

Error in Untitled (line 6)
F = (s+10)/(s^3+45*s^2-250^s);

Answer 1

[Star Strider]

This could be a problem:

F = (s+10)/(s^3+45*s^2-250^s)
                          ↑

I doubt that ‘250^s’ is supported.

Did you perhaps intend:

F = (s+10)/(s^3+45*s^2-250*s)

that produces the appropriate transfer fucntion?

[Giovanni Salviati]

I'm so stupid.

Yes it's the second transfer function the right one.

[Star Strider]

You’re not stupid!

You just made a typographical error, and confirmed that you’re just like all the rest of us! I’ve spent more time than I want to admit to in tracking down typographical errors in my own code, that I didn’t immediately see.

Answer 2

[Maja Bakalarz]

Hi,

I have similar problem but according to equation

I can't remove s from the power.

I had to define s earlier by this: s=tf('s') and now if I can type this equation in different way to get the score that I need?

I would be very grateful for help

[Star Strider]

The exponential term is correct. It is actually coded as an 'InputDelay' in the transfer function properties.

To illustrate —

k   = 3;
T_2 = 5;
tau = 7;

s = tf('s');
G_2 = k/(1 + T_2*s) * exp(-tau*s)

G_2 =
 
                 3
  exp(-7*s) * -------
              5 s + 1
 
Continuous-time transfer function.

G_2.InputDelay

ans = 7

figure
step(G_2)
grid

.

[Maja Bakalarz]

Thank you! Now everythin is working!

[Star Strider]

My pleasure!