Seasonal plot of daily data

Hi All,

I have daily closing prices of a particular commodity. I would like to generate annual plot of the series so as to get a visual feel of the seasonality across years. 

For ex I have crude oil daily price data since 2002. I would like to have multiple lines on a single plot, each line represents each year and plotted against day of year on x-axis. I tried reading the data as zoo or xts objects, but unable to plot multiple series on a single plot. Can any one help me out in this regard?

Thanks in advance for the help, rgds

SNVK