excel - Finding maximum value in range containing same value -

i have data:

       b 1       100 1       300 1       200 2       100 2       500 3       100 3       300 3       200 

i want select maximumof(b) same value in column1. output should be:

       b       c 1       100     300 1       300     300 1       200     300 2       100     500 2       500     500 3       100     300 3       300     300 3       200     300 

i have tried:

={max(if(a:a=a1,b:b))}   

this gives me maximum value 1 i.e. 300.

how can copy formula other group of cells? gives message you can not move array values.
how can achieve this?

i suggest delete columnc , start again - using formula in c1. either drag c1 down far required or copy , past c2:c whatever. make sure = inside curly brace.