Undefined function or variable 'dfdes'

I am trying to use these commands to find the transfer function for elliptic filter, I know i can use other matlab command but i want to use these commands to order to obtain precise results. Can someone explain what am i doing wrong.

[Stephen23]

Mirza Baig's "Answer" moved here:

i copied the whole thing matlab and i got this error.. do i need to define this function? or something else. any help would be much appreciated

Answer 1

[Stephen23]

You need to define those functions yourself, or get them from someone else. They are not inbuilt MATLAB functions.

The screenshots you show appear to contain only the help and not the complete function code, so you cannot copy-and-paste. You will have to ask the authors to provide that code for you. Or search the interweb and see if someone else has uploaded a copy.

But you certainly cannot expect that code that is not anywhere on your computer will magically be able to be called by MATLAB.