Convert a digital filter to transfer function

I have a coefficients of FIR filter ,found it by 'fir1' function, in general, i want to convert a digital filter to transfer function with apply this formula :

The method :

Design a 48th-order FIR filter passband , with a cutoff frequency w=[0.35 0.65]. Compute the coefficients of the equivalent transfer function.

   % Coefficients of fir filter
   c = fir1(48,[0.35 0.65]);

   %Filter Transfer Function
    [b,a] = tf(c);

The error found:

    Error using tf
    Too many output arguments.

How can i solve this problem? how can i find a transfer function of fir filter with this specifications?

Answer 1

[Stephan]

Hi,

tf has only one output - use:

% Coefficients of fir filter
c = fir1(48,[0.35 0.65]);
%Filter Transfer Function
trans_fun = tf(c);

Best regards

Stephan

[Sandi J]

Thank you for your reply ,but what is the difference between this case and the case in this page https://www.mathworks.com/help/signal/ref/tf.html

[Stephan]

I think it is the type of input. The result of fir1 is a row vector which is input for tf.

The input of the link you provided is a digital filter object.

I think the tf function make a case distinction and changes behavior depending on the input type.