Ruby: inject issue when turning array into hash

Question

a = [[1, \'a\'],[2, \'b\'],[3, \'c\'], [4, \'d\']]
a.inject({}) {|r, val| r[val[0]] = val[1]}

When I run this, I get an index error

When I change the b

Answer 1

a.inject({}) { |r, val| r.merge({ val[0] => val[1] }) }