zepo (System Identification Toolbox)

Describe the zeros and pole format.

help zepo

Description

The zepo format is created by th2zp and zp and used by zpplot. It contains information about zeros and poles and their standard deviations. The internal format is intended to be transparent to the user. The basic way to display the information is to use the zpplot command. Some specific infor-mation is retrieved from the format by the function getzp. This entry gives the details of the internal representation, but this information is not necessary for most users of the System Identification Toolbox.

The first row of the matrix consists of integers that give information about what the column below contains. The integers are coded in the following way:

The zeros associated with input number ku and output number ky correspond to the number (ky - 1)*1000 + ku. The standard deviations of these zeros correspond to the number
(ky-1)*1000 + ku +60.
The poles associated with input number ku and output number ky correspond to the number (ky - 1)*1000 + ku + 20.
The standard deviation of these poles correspond to the number
(ky - 1)*1000 + ku + 80.
The zeros associated with noise input number ky and output number ky (only these are normally represented) correspond to the number 500 + ky.
The standard deviation of these, the corresponding poles, and their standard deviations are obtained by adding 60, 20, and 80, respectively to this number.
Positions corresponding to nonexisting zeros and poles (as well as zeros and poles at infinity) are represented by inf.
If any of the above numbers is negative, it indicates that the pole or zero representation corresponds to a continuous-time model. Then the absolute value of the number has the interpretation above.
For complex conjugated pairs, the first row in the corresponding entry for the standard deviation contains a complex number whose real and imaginary parts are the standard deviations of the real and imaginary parts, respectively, of the pole or zero in question. The next row entry (corres-ponding to the conjugate pole or zero) contains a real number that is the correlation between the real and imaginary parts.