I was not quite sure what to call this. What I need to do is take table which looks like the
following that looks like the following

year amount cat
1990 1900 a
1990 500 b
1990 300 c
1991 1500 a
1991 600 b
1991 100 c
.

and create a table that looks like

year a b c
1990 1900 500 300
1991 1500 600 100
,

what is the best way to do this?