Question

I have an array in Ruby which looks like this:

@arr = [ [2.1, pass], 
         [2.1, fail],
         [2.1, pass],
         [2.1, unknown],
         [2.1, pass],
         [3.0, pass],
         [3.0, unknown],
         [3.1, pass],
         [3.1, fail] ]

I want to apply some kind of hashing or computation on it such that my output should be an array like:

@result = [ [2.1, 3, 1, 1],
            [3.0, 1, 0, 1],
            [3.1, 1, 1, 0] ]

The output array displays results in this format {version, no.of pass, no.of fail, no.of unknown}

Answer 1

If I translate your expression a bit…

@arr = [
  [2.1, :pass],
  [2.1, :fail],
  [2.1, :pass],
  [2.1, :unknown],
  [2.1, :pass],
  [3.0, :pass],
  [3.0, :unknown],
  [3.1, :pass],
  [3.1, :fail]]

Then the problem can be solved with…

@arr.group_by(&:first).values.map do |x|
  y = x.flatten
  [y[0], y.count(:pass), y.count(:fail), y.count(:unknown)]
end