I want to get all the keys with the max value.
# I want 6 and 2 since they both of them occurred three times.
arr = [5, 6, 2, 1, 2, 5, 6, 6, 2]
I tried this but it returns 6 only.
# this returns {5=>2, 6=>3, 2=>3, 1=>1}
freq = hash.inject(Hash.new(0)){ |h, v| h[v] += 1; h }
# then I use max_by, but this gives only 6
p arr.max_by{ |v| freq[v]}
I would propose a group_by on the number of occurrences of unique values in the original Array, followed by taking the values of the mapping with the highest number:
arr = [5, 6, 2, 1, 2, 5, 6, 6, 2]
arr.uniq.group_by { |v| arr.count(v) }.max.last
# [6, 2]
The group_by yields a Hash with the number of occurrences as keys and unique elements of arr with that number of occurrences as values. The .max call will then yield the mapping with the highest key, and .last will take only the values which we were interested in.
[1] instead of .last, is more coherent with I want the second value of an array converted from an hash, instead of I want the last element of an array
What about
arr = [5, 6, 2, 1, 2, 5, 6, 6, 2]
uniques = arr.uniq
max_count = uniques.map { |v| arr.count(v) }.max
max_values = uniques.select { |v| arr.count(v) == max_count }
#=> [6, 2]
I think as
arr.group_by(&:to_i).each_with_object({}) do |(k,v),h|
(h[v.size] ||= []) << k
end.max_by(&:first).last # => [6, 2]
arr = [5, 6, 2, 1, 2, 5, 6, 6, 2]
freq = arr.inject(Hash.new(0)) { |h, v| h[v] += 1; h }
max = freq.max[1]
freq.keep_if { |h, v| v == max }.keys
# => [6, 2]
The code is pretty self explanatory. I'm just using your code up until freq.keep_if. freq.max returns an array in the form [6, 3] (6 being the number, 3 being the occurrences), so freq.max[1] is the number of occurrences. .keys returns all the keys in an array, which gets rid of the occurrences.
