CODEWITHSUNDEEP
rubyarrays
Luigi
Luigi

Reputation: 5603

Ruby count range of values in an array

I have an array:

[1,2,3,4,5,6,7,8,9,10]

and I need to count three separate things.

1) All values less than or equal to 6.

2) All values equal to 7 or 8.

3) All values greater than 8.

What is the best way to do this without counting individual values and adding them all together?

Upvotes: 1

Views: 2446

Answers (4)

Cary Swoveland
Cary Swoveland

Reputation: 110675

More interesting, imo, is to answer @Luigi's three questions with a single statement (containing no semicolons). Here are two ways to do it:

a = [1,2,3,4,5,6,7,8,9,10]

a.inject([0,0,0]) {|arr,i| [arr[0]+(i<7 ? 1:0), arr[1]+((i>6 and i<9) ? 1:0), arr[2]+(i>8 ? 1:0)]}
a.slice_before(7).to_a.map {|arr| arr.slice_before(9).to_a}.flatten(1).map(&:size)
    # => [6, 2, 2]

Edit: another, inspired by @staafl's answer:

arr.group_by {|e| (e+1)/2-4<=>0}.values.map(&:size)

Can you suggest others?

Upvotes: 0

staafl
staafl

Reputation: 3225

How about this:

>> hash = Hash.new(0)
>> arr = [1,2,3,4,5,6,7,8,9,10]
>> arr.each { |e| hash[(e-7.5).truncate<=>0]+=1 }
>> hash
=> {-1=>6, 0=>2, 1=>2}

Or even more succinct:

>> arr = [1,2,3,4,5,6,7,8,9,10]
>> arr.each_with_object(Hash.new(0)) { |e,h| h[(e-7.5).truncate<=>0]+=1 }
=> {-1=>6, 0=>2, 1=>2}

Upvotes: 0

zeantsoi
zeantsoi

Reputation: 26193

arr = [1,2,3,4,5,6,7,8,9,10]

arr.select {|e| e <= 6}.size
#=> 6

arr.select {|e| e == 7 || e == 8}.size 
#=> 2

arr.select {|e| e > 8}.size 
#=> 2

Upvotes: 1

squiguy
squiguy

Reputation: 33370

Use Enumerable#count with a block.

[1,2,3,4,5,6,7,8,9,10].count { |val| val <= 6 }
[1,2,3,4,5,6,7,8,9,10].count { |val| val == 7 || val == 8 }
[1,2,3,4,5,6,7,8,9,10].count { |val| val > 8 }

Upvotes: 3

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