I'm trying to plot the average price of Bitcoin of the last 3 year with R. I was able to get the data into the console box but I don't know how to select a specific column for plotting a graph. I haven't used R for a long time so I forgot how to do that, I remember how to plot the graph though, so I just need help with selecting the data I need.

read.csv('http://www.quandl.com/api/v1/datasets/BITCOIN/MTGOXUSD.csv?&trim_start=2010-07-17&trim_end=2013-12-13&collapse=monthly&sort_order=desc', colClasses=c('Date'='Date'))


Thanks!