function  [r,ricker]=calrick(dt,tmin,fr) 
t=(-tmin*2.2):dt:tmin*2.2;
ricke=(1-t .*t * fr^2 *pi^2  ) .*exp(- t.^2 * pi^2 * fr^2 ) ;
r=length(ricke);ricker(1:r)=ricke(1:r);
plot([1:length(ricker)]*dt,ricker);
title('Ricker Wavelet Source Function');xlabel('Time (s)');    
