[num,den]=​series(n1,​d1,n2,d2,n​3,d3); please tell me that in this line which error??

[num,den]=series(n1,d1,n2,d2,n3,d3);

[Star Strider]

Context: series ‘Series connection of two models’

Please use the ‘Products’ tags.

Answer 1

[Les Beckham]

As the documentation linked to by Star Strider indicates, series is meant to connect two models. So you will need to call the series command twice to connect your three models. Also, the num/den syntax is deprecated/obsolete and may be removed in future Matlab releases. Ideally you should define transfer function objects from your numerators and denominators.

Try this using your n1/d1, n2/d2, and n3/d3:

sys1 = tf(n1, d1)
sys2 = tf(n2, d2)
sys3 = tf(n3, d3)
sys12 = series(sys1, sys2)
sys123 = series(sys12, sys3)

[anjalee kumari]

from this method we get step and impulse response of system is same and ramp is change so this is possible that step and impulse response of is same?

Answer 2

[John D'Errico]

There is no error at all. That is perfectly correct MATLAB syntax, for some (possibly unknown) general function named series.

So we cannot possibly tell you what is the "error".

In general, if you get an error in MATLAB, and want help, then read the error message. If you cannot understand the error message, then ask here, but post the COMPLETE error text, everything that was generated by MATLAB. As well, show how you called the function that caused the problem. Otherwise we cannot very easily help you, since we do not know what you did wrong.

If you think that this is correct syntax for the series function from the symbolic toolbox, I'd want to suggest that you are wrong. The series function expects you to pass in a function. Not a list of numerical values. Not a list of numbers in any form. The sym TB series function also does not return a separate numerator and denominator as outputs.

You might want to read the help for series. Or if you have some other function by that same name, then contact the source of the code. Or read the help, if any was provided.

[anjalee kumari]

i don't understand from the help command also.... so i will send here the code and the error

[anjalee kumari]

n1=[2 3];
d1=[1 0 0 0];
n2=[4/5];
d2=[1 3];
n3=[1 0 0];
d3=[1 -6];
[num,den]=series(n1,d1,n2,d2,n3,d3);
step(num,den);
grid on
title('15-TC-42')

>> lb4ex2
Error using series (line 98)
Wrong number of input arguments for obsolete matrix-based syntax.

Error in lb4ex2 (line 7)
[num,den]=series(n1,d1,n2,d2,n3,d3);

[John D'Errico]

What version of MATLAB are you using?

Anyway, this is not the error I get when I try your code.

When you do a which series, what do you see? My system shows this:

which series -all
/Applications/MATLAB_R2016b.app/toolbox/symbolic/symbolic/@sym/series.m  % sym method

[anjalee kumari]

R2013a versin of matlab i 'll use