function[ikstararr]=ikstar(dx,dy,kxdx,kydy,spmeth) %spmeth=0 second order upwind if spmeth==0 ikstararr=zeros(1,4); %Forward Differencing on x ikstararr(1)=(-3+4*exp(i*kxdx)-exp(2*i*kxdx))/(2*dx); %Backward Differencing on x ikstararr(2)=(3-4*exp(-i*kxdx)+exp(-2*i*kxdx))/(2*dx); %Forward Differencing on y ikstararr(3)=(-3+4*exp(i*kydy)-exp(2*i*kydy))/(2*dy); %Backward Differencing on y ikstararr(4)=(3-4*exp(-i*kydy)+exp(-2*i*kydy))/(2*dy); end %spmeth=1 if spmeth=1 ikstararr=zeros(1,2); %