function [x_out]=netcdf_ecco_GenericgridRotateLon(x_in,lon0_in,lon0_out,lonSyst);

%lonSyst=1: we use degree east from greenwich
%lonSyst=2: we use degree east/west from greenwich

%-this routine first set longitude according to lonSyst
%and then change the 0 longitude from lon0_in to lon0_out
%-input:	lon0_in is the current 0 longitude, in degree east from greenwich
%		lon0_out is the new 0 longitude, in degree east from greenwich
%		x_in is longitude relative to lon0_in
%output:	x_out is longitude relative to lon0_out

if lonSyst==2
	tmp1=find(x_in>=180); x_in(tmp1)=x_in(tmp1)-360;
        tmp1=find(x_in<-180); x_in(tmp1)=x_in(tmp1)+360;
elseif lonSyst==1
        tmp1=find(x_in<0); x_in(tmp1)=x_in(tmp1)+360;
        tmp1=find(x_in>=360); x_in(tmp1)=x_in(tmp1)-360;
else
fprintf('lonSyst must be 1 or 2 => stop \n'); return; end;
x_out=x_in-(lon0_out-lon0_in);
if lonSyst==2
        tmp1=find(x_out>=180); x_out(tmp1)=x_out(tmp1)-360;
        tmp1=find(x_out<-180); x_out(tmp1)=x_out(tmp1)+360;
elseif lonSyst==1
        tmp1=find(x_out<0); x_out(tmp1)=x_out(tmp1)+360;
        tmp1=find(x_out>=360); x_out(tmp1)=x_out(tmp1)-360;
end