function [cost,d_model]=cost_beam(q0,time,d_data)
%cost function for the vibrating beam inverse problem
%requires a vector of parameters, time and collected data
C=q0(1);
K=q0(2);
%  vval=q0(3);
%  x0=[q0(3) 0]; %initial conditions
x0=[d_data(1) 0]; %initial conditions
% [t,x]=ode23(@ode_model,time,x0,[],C,K); %solve the mass-spring dashpot model
 x=exp(-C*time/2)*d_data(1).*cos(sqrt(4*K-C^2)*time/2);
d_model=x(:,1); %want postion of the beam
cost=sum((d_data-d_model).^2)*100; %calcutate cost function