array-hash.rb

[
{
	name: "Group 1"
	data: [1,2,3,4]
},
{
	name: "Group 2"
	data: [1,2,3,4]
}
]

result.rb

@groups.collect { |g| { name: g.name, data: g.task_trans.group_by_month(:start_date,   range: @range, format: "%b %Y").count } }

and got this result

[
  {:name=>"Grupo 1",
  :data=>
    {"Nov 2015"=>6,
    "Dic 2015"=>8}},
  {:name=>"Grupo 2",
  :data=>
    {"Nov 2015"=>0,
    "Dic 2015"=>6}}
]