up_ixf crashes

up_ixf crashes

Bug report and fix.

upcom does not correctly check how Up.copt(1,8) (default step length) is filled. As a result up_ixf tends to crash.

You can correct the problem by setting a step value to 1. For example, run the demo_up demo and continue with the commented lines

   b=fe_c(mdof,XFdof(1,1))'; c=fe_c(mdof,XFdof(:,1));
  indw = [1:40:600];
  upcom(';opt model 1;opt omethod 3;opt gprint 0')
  Up.copt(1,8)=1;  % this is a simple fix to the bug
  upcom('parcoef',[1 1 1]);coef = up_ixf('basic',b,c,IIw,IIxf,indw);

The reason the use of up_ixf is commented out in the demo is that the algorithm is really not very good. upcom can be used for practical FRF based updating but the associated algorithms are not currently included in the SDT.