Generate the vertical bar chart that summarizes all grain production for all countries for both years. DISCRETE creates a separate bar for each unique value of YEAR. GROUP= groups the bars by country. To create a legend for midpoint values, SUBGROUP= is assigned the chart variable. GSPACE= controls the space between the groups of bars. 
proc gchart data=newgrain;
     format country $country.;
     vbar3d year / discrete
                   sumvar=megtons
                   group=country
                   subgroup=year
                   legend=legend1
                   space=0
                   width=5
                   gspace=5
                   maxis=axis1
                   raxis=axis2
                   gaxis=axis3
                   cframe=grayaa
                   coutline=black