Ruby Array to Histogram. How to group numbers by range? -

i need group array values range-based histogram in ruby...

values = [ 139, 145, 149, 151, 152, 153, 163, 166, 169 ] 

for example:

141 - 145 = 2 146 - 150 = 1 151 - 155 = 3 

...

is there simple way use group_by?

to prepare histogram 1 specifies smallest value of first range, range size , number of ranges. pre-processing of data may necessary determine values. example, given

values = [139, 145, 149, 151, 152, 153, 164, 166, 169] group_size = 5 

we might compute smallest value of first group , number of groups follows:

smallest, largest = values.minmax   #=> [139, 169]  start = group_size*(smallest/group_size)   #=> 135  nbr_groups = ((largest-start+1)/group_size.to_f).ceil   #=> 7  

we can construct array can use create histogram.

def group_values(values, start, nbr_groups, group_size)   groups = array.new(nbr_groups) |i|     f = start + * group_size     { nbr: 0, range: f..f+group_size-1 }   end       values.each_with_object(groups) { |v,arr|     arr[(v-start)/group_size][:nbr] += 1 } end 

let's try (for values of start , nbr_groups computed above).

freq = group_values(values, start, nbr_groups, group_size)   #=> group_values(values, 135, 7, 5)   #=> [{:nbr=>1, :range=>135..139},   #    {:nbr=>0, :range=>140..144},   #    {:nbr=>2, :range=>145..149},   #    {:nbr=>3, :range=>150..154},   #    {:nbr=>0, :range=>155..159},   #    {:nbr=>1, :range=>160..164},   #    {:nbr=>2, :range=>165..169}] 

note that

• the value of :range each element of resulting array provided labeling horizontal axis of histogram.
• i initialized array groups groups containing no elements of values (for values 140-144 , 155-159) included in array returned. had constructed array on fly not have contained hashes 2 groups.
• to establish range of frequencies vertical axis of histogram might compute following.

freq.map { |h| h[:nbr] }.minmax   #=> [0, 3]