fitfrd
Fit frequency response data with state-space model
Syntax
B = fitfrd(A,N) B = fitfrd(A,N,RD) B = fitfrd(A,N,RD,WT)
Description
B = fitfrd(A,N)
is a state-space object with
state dimension N, where A
is an frd
object and
N is a nonnegative integer. The frequency response of
B
closely matches the D-scale frequency
response data in A
.
A
must have either 1 row or 1 column, although it need not be
1-by-1. B
will be the same size as A
. In all
cases, N
should be a nonnegative scalar.
B = fitfrd(A,N,RD)
forces the relative degree
of B
to be RD
. RD
must be a
nonnegative integer. The default value for RD
is 0. If
A
is a row (or column) then RD
can be a vector
of the same size as well, specifying the relative degree of each entry of
B
. If RD
is a scalar, then it specifies the
relative degree for all entries of B
. You can specify the default
value for RD
by setting RD
to an empty
matrix.
B = fitfrd(A,N,RD,WT)
uses the magnitude of
WT
to weight the optimization fit criteria. WT
can be a double, ss
or frd
. If
WT
is a scalar, then it is used to weight all entries of the
error criteria (A-B
). If WT
is a vector, it must
be the same size as A
, and each individual entry of
WT
acts as a weighting function on the corresponding entry of
(A-B
).
Examples
Limitations
Numerical conditioning problems arise if the state order of the fit
N
is selected to be higher than required by the dynamics of
A
.
Version History
Introduced before R2006a