function y=unpack_param(x)
% y=unpack_param(x)
%
% Create a 2D parameter array from the 'compressed' parameter array x
% Parameter format: a 3-row matrix with the parameter specification
%  - line number on first row
%  - column number on second row
%  - parameter value on third row
% this function will generate a symmetric parameter matrix of the
% appropriate size

center(1)=max(abs(x(1,:)))+1;
center(2)=max(abs(x(2,:)))+1;
y=zeros(2*center(1)-1,2*center(2)-1);
y(center(1),center(2))=1;

for i=1:size(x,2),
  y(center(1)+x(1,i),center(2)+x(2,i))=x(3,i);
end
