Max value of nested array in hash

Question

What I have:

hash = {id =>[string, number], id =>[string, number]}

I need to get the max value of number. I have been able to do this, but when I puts it. I get:

id
string
number

What I need please

id string number

This is what I've tried:

This brings the max value to the top of list, but I need to exclude the rest of the list.

hash.each{|x, y| puts "#{x} #{y[0]} #{y[1]}"}.max

This returns the max value but displays it vertically

puts hash.max_by{|y| "#{y}"}

I have tried numerous other things and am having a hard time wrapping my head around this one.

Not sure if it matters but I am read this in from a file into a hash, the number is a float

I expect you realize that hashes have unique keys, and most readers probably know what your hash looks like, but you should write it like (for example) this: hash = {id1 =>[string1, number1], id2 =>[string2, number2]}. — Cary Swoveland
– Cary Swoveland, Commented Nov 18, 2013 at 4:27

Andrew Marshall · Accepted Answer · 2013-11-18 03:14:35Z

4

The max here doesn’t do anything (since it is called on hash and its return value never used):

hash.each{|x, y| puts "#{x} #{y[0]} #{y[1]}"}.max

This is the same as doing puts on an array (since that’s what max_by returns), which prints each element on a separate line. You’re also unnecessarily converting your number to a string (which can result in unexpected comparison results):

puts hash.max_by{|y| "#{y}"}

Instead let’s just get the max key/value pair:

max = hash.max_by { |id, (string, number)| number }
#=> ["the-id", ["the-string", 3.14]]

Now we can flatten and join the array before puts-ing it:

puts max.flatten.join(' ')
# prints: the-id the-string 3.14

answered Nov 18, 2013 at 3:14

Andrew Marshall

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6 Comments

user2963093 Over a year ago

Wow! I didn't realize that in the block I could do |id,(string, number)|. Only problem is that I added new items with a higher number but with a lower index to the hash and what it is doing is giving me the max index instead of the value.

user2963093 Over a year ago

Sorry I mean with a lower "id" and a higher "number"

user2963093 Over a year ago

Thanks man you really helped me. I didn't realize that I could put the |id,(string, number)| in block like that. So this is what I did. hash.each do |id,(string, number)| max = "#{id}. #{string}, #{number}" end puts max

Andrew Marshall Over a year ago

You said “max value of number“ in your question, but your comment seems to contradict that. Stop using each when you can use a higher-order function. Your each in your comment will just get the last key inserted into hash (along with its value), not necessarily the max of anything.

Andrew Marshall Over a year ago

@user2963093 No, it really doesn’t. See ideone.com/SaMvu4 for example. Note how the “max” value is in fact not in any way the max.

|

Andrew Marshall · Accepted Answer · 2013-11-18 03:19:39Z

0

I would re-arrange the hash with number as the key, then use sort_by(): http://www.rubyinside.com/how-to/ruby-sort-hash

edited Nov 18, 2013 at 3:19

Andrew Marshall

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answered Nov 18, 2013 at 3:19

Geremy

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