massign (Mu Analysis and Synthesis Toolbox)

Mu Analysis and Synthesis Toolbox

massign

Matrix assignment for VARYING and SYSTEM matrices

Syntax

out = massign(matin,rowindex,colindex,data)

Description
Performs a matrix assignment like operation on VARYING and SYSTEM matrices. It is functionally equivalent to:

matin(rowindex,colindex) = data

where rowindex and colindex are vectors specifying the rows and columns (or outputs and inputs if matin is a SYSTEM) to be changed.

data must either be a constant or of the same type as matin. The dimensions of data must be consistent with the lengths of rowindex and colindex.

Note: when applied to a SYSTEM, the result will almost always be nonminimal.

Examples
In the first example a VARYING matrix with two independent variables is formed with identical (and obvious) data for each matrix.

tl = [11,12,13,14;
21,22,23,24;
31,32,33,34;
41,42,43,44];

vmat = vpck([tl;tl],[0.1,0.2]);

Now make a 2 x 2 data matrix and insert it into the VARYING matrix. Changing the order of the row and column indices has the effect of permuting the result. This is identical to the constant matrix case.

ri = [1,3];
ci = [4,2];
data = [0.001, 0.002; 0.003, 0.004];
vmatl = massign(vmat,ri,ci,data);
see(vmatl)
4 rows                   4 columns
iv = 0.1
11.0000    0.0020    13.0000    0.0010
21.0000   22.0000    23.0000   24.0000
31.0000    0.0040    33.0000    0.0030
41.0000   42.0000    43.0000   44.0000

iv = 0.2
11.0000    0.0020    13.0000    0.0010
21.0000   22.0000    23.0000   24.0000
31.0000    0.0040    33.0000    0.0030
41.0000   42.0000    43.0000   44.0000

In the following example part of a system is replaced by the massign function. The initial system is a diagonal system of first order lags. The 2,2 element is replaced by a lightly damped system and the result plotted. Note that the modified system is no longer minimal.

a = diag([1,2,-3,-4]);
b = eye(4);
c = diag([1,2,3,4]);
sys = pck(a,b,c);
subsys = nd2sys(1,[1,0.1,1]);
sys = massign(sys,2,2,subsys);
minfo(sys)
system: 10 states                 4 outputs4 inputs
omega = logspace(-1,2,100);
sys_g = frsp(sys,omega);
vplot('liv,lm',sys_g,'-')

See Also
sel

madd, msub mfilter