how to write the command for numerator and denominator polynomial coefficients

I want to find the transfer function. how to write the command for numerator and denominator polynomial coefficients: num=[1 0 .......0 n1];?? den=[1 0......0 n2];?? for a large n1=500,n2=890.

[David Goodmanson]

Hi phoenix, this is really a case where you should go to the help for polyval and possibly the documentation for polyval. It shows all you need to know to do this.

[Walter Roberson]

I was certain that I had seen someone answer in terms of ones() ??

[phoenix]

yeah but i dont know why it is not showing.Please type the commands for me.

[Walter Roberson]

num = [1, zeros(1,n1)];
den = [1, zeros(1,n2)];
tf(num, den)

[phoenix]

Thanks for the code.how to plot the magnitude of the following transfer function(attached)

Answer 1

[Sammit Jain]

Agree with Walter on the method using tf.

So this is basically what you can do:

% Initialize n1 and n2
n1 = 500;
n2 = 890;

% Initialize num and den as a vector of zeros
num = [1, zeros(1,n1-1)];
den = [1, zeros(1,n2-1)];

% Give values to num and den
% Your code here

% Use the num and den values to calculate the transfer function
tf(num,den)

[phoenix]

how to plot the magnitude of the following transfer function(attached)

[Walter Roberson]

You cannot do that as a proper transfer function because of the sqrt() .

Under a couple of assumptions you can do a change of variables to get 25*z^9/(z^44-15*z^12-22) . You can use standard pole/zero plotting on that -- but only for z > 0. Under that condition there is one pole at about 1.10127776334121 (the other poles are at negative or complex z, and for those the simplifications to get that polynomial are not valid.)