[R] FW: help with time Series regression please

[snowcat wong]

Dear all,
 
I am having difficulty to built a model of quarter sales of spirits data, and deciding which is the best model. The yfit2, yfit3, and yfit4 lines was not appeared right at the end. The data and script is enclosed with this email.
 
I am using the harmonic regression model to exam the periodogram of the residuals. I am not sure this step is right or not? Which is the best formula to analysis the trend and seasonality for this data set? AR, MA or ARMA and how to decide?  
 
Please help!!
 
many thanks and regard,
Cathy Wong
 
  		 	   		  
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