[Ixbar,Iybar,Ixybar]=shftprop ...

function [Ixbar,Iybar,Ixybar]=shftprop ...
         (A,xbar,ybar,Ix,Iy,Ixy)
%
% [Ixbar,Iybar,Ixybar]=shftprop ...
%   (A,xbar,ybar,Ix,Iy,Ixy)
% ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
% Use parallel-axis theorem to shift properties
% relative to centroidal axis.
%
% A      - area of polygon
% xbar   - x coordinate of centroid
% ybar   - y coordinate of centroid
% Ix     - inertia about y axis
% Iy     - inertia about x axis
% Ixy    - product of inertia
%
% Ixbar  - inertia about y axis - shifted
% Iybar  - inertia about x axis - shifted
% Ixybar - product of inertia - shifted
%
% User m functions called:  none
%----------------------------------------------

Ixbar=Ix-A*ybar^2; Iybar=Iy-A*xbar^2;  
Ixybar=Ixy-A*xbar*ybar;