How can I enter a transfer function without writing down the exponents?

Is there a possibility to enter transfer functions like this one:

without writing out the exponent?

I know that it could be inserted as:

num=[35 3.5 8.75];
den=[100 25 100.24 1];
sys=tf(num,den)

but writing out equations could be time consuming so is there a faster way?

Answer 1

[Stephan]

Hi,

i think you made a mistake by multiplying the denumerator - When i calculate by hand i get:

num=[35 3.5 8.75] 
den = [100 25 100.24 1]

For your purposes you could tryout conv function - it multiplies 2 polynomials:

num1 = [8.75];
num2 = [4 0.4 1];
den1 = [100 1];
den2 = [1 0.24 1];

sys = tf(conv(num1,num2),conv(den1,den2))

sys =

        35 s^2 + 3.5 s + 8.75
    ------------------------------
    100 s^3 + 25 s^2 + 100.2 s + 1

Continuous-time transfer function.

Best regards

Stephan

Answer 2

[dpb]

num=8.75*[4 0.4 1];
den=conv([100 1]),[1 0.24 1]);

convolution of polynomial coefficient vectors is same as multiplication. NB: the hand multiplication above for the denominator is in error; the actual answer is

>> conv([100 1],[1  0.24 1])
ans =
100.0000   25.0000  100.2400    1.0000
>>