gistfile1.txt

log = [
  {time: 201201, x: 2},
  {time: 201201, y: 7},
  {time: 201201, z: 2},
  {time: 201202, a: 3},
  {time: 201202, b: 4},
  {time: 201202, c: 0}
]

I want to collapse the array of hashes into this, all the hashes with the same time: should be merged into one.

[
  {time: 201201, x: 2, y: 7, z: 2},
  {time: 201202, a: 3, b: 4, c: 0},
]

My solution seems to work, but its functional, it wont work if another element is added to the array.
results = []
while log do
  elt1 = log.select {|x| x[:time] == 201201 }
	elt2 = log.select {|x| x[:time] == 201202 }
	results << elt1[0].merge(elt1[1].merge(elt1[2]))
	results << elt2[0].merge(elt2[1].merge(elt2[2]))
	break
end
results

log = [
  {time: 201201, x: 2},
  {time: 201201, y: 7},
  {time: 201201, z: 2},
  {time: 201202, a: 3},
  {time: 201202, b: 4},
  {time: 201202, c: 0}
]

log_hashes = Hash.new { |h, k| h[k] = { time: k } }
log.each do |log_line|
  log_hashes[log_line[:time]].merge!(log_line)
end

log = log_hashes.values
# End result: [{:time=>201201, :x=>2, :y=>7, :z=>2}, {:time=>201202, :a=>3, :b=>4, :c=>0}] 

To get you started

a = log.select {|x| x[:time] == 201202}
x = {}
a.each { |arr| x.merge! arr }