Find highest value from hash that contains "nil" - ruby

Question

I have a hash which looks like this
#hash = {
0=>[{"name"=>"guest", "value"=>7.9}],
1=>[nil], 2=>[nil], 3=>[nil], 4=>[nil], 5=>[nil], 6=>[nil], 7=>[nil], 8=>[nil],
9=>[nil], 10=>[nil], 11=>[nil], 12=>[nil], 13=>[nil], 14=>[nil], 15=>[nil],
16=>[nil], 17=>[nil], 18=>[nil],
19=>[{"name"=>"test", "value"=>2.5}],
20=>[{"name"=>"roam", "value"=>2.5}],
21=>[{"name"=>"test2", "value"=>1.58}],
22=>[{"name"=>"dff", "value"=>1.9}],
23=>[{"name"=>"dddd", "value"=>3.16}]
}
I want the highest value from this hash in a variable. The output should be
#h = 7.9 \\only float value which should be highest among all
so I am doing like this
#hash.each do |k, v|
if !v.nil?
#h= [v.flatten.sort{ |v1, v2| v2['value'] <=> v1['value'] }.first['value']]
end
end
but sometimes it works, and most of the times it doesn't.

Answer 1

#hash.values.flatten.compact.map { |h| h["value"] }.max
=> 7.9
Which equates to:
Get the values of the hash as an array
Flatten all the elements in the values array
Compact to remove all nil entries
Map the remaining entries to the ["value"] element in the hash
Return the maximum of all those value
It makes a lot of assumptions about the format of your #hash though.

Answer 2

I prefer #Shadwell's solution, but here's another way:
hash.select { |_,v| v.first }
.max_by { |_,v| v.first["value"] }
.last
.first["value"]
#=> 7.9
The steps (with all but one n=>[nil] element removed for readabiity):
hash = { 0=>[{"name"=>"guest", "value"=>7.9}],
1=>[nil],
19=>[{"name"=>"test", "value"=>2.5}],
20=>[{"name"=>"roam", "value"=>2.5}],
21=>[{"name"=>"test2", "value"=>1.58}],
22=>[{"name"=>"dff", "value"=>1.9}],
23=>[{"name"=>"dddd", "value"=>3.16}]}
h = hash.select { |_,v| v.first }
#=> { 0=>[{"name"=>"guest", "value"=>7.9}],
# 19=>[{"name"=>"test", "value"=>2.5}],
# 20=>[{"name"=>"roam", "value"=>2.5}],
# 21=>[{"name"=>"test2", "value"=>1.58}],
# 22=>[{"name"=>"dff", "value"=>1.9}],
# 23=>[{"name"=>"dddd", "value"=>3.16}]}
a = h.max_by { |_,v| v.first["value"] }
#=> [0, [{"name"=>"guest", "value"=>7.9}]]
b = a.last
#=> [{"name"=>"guest", "value"=>7.9}]
b.first["value"]
#=> 7.9