Pull min and max value from CSV file - ruby

Question

I have a CSV file like:
123,hat,19.99
321,cap,13.99
I have this code:
products_file = File.open('text.txt')
while ! products_file.eof?
line = products_file.gets.chomp
puts line.inspect
products[ line[0].to_i] = [line[1], line[2].to_f]
end
products_file.close
which is reading the file. While it's not at the end of the file, it reads each line. I don't need the line.inspect in there. but it stores the file in an array inside of my products hash.
Now I want to pull the min and max value from the hash.
My code so far is:
read_file = File.open('text.txt', "r+").read
read_file.(?) |line|
products[ products.length] = gets.chomp.to_f
products.min_by { |x| x.size }
smallest = products
puts "Your highest priced product is #{smallest}"
Right now I don't have anything after read_file.(?) |line| so I get an error. I tried using min or max but neither worked.

Answer 1

Without using CSV
If I understand your question correctly, you don't have to use CSV class methods: just read the file (less header) into an array and determine the min and max as follows:
arr = ["123,hat,19.99", "321,cap,13.99",
"222,shoes,33.41", "255,shirt,19.95"]
arr.map { |s| s.split(',').last.to_f }.minmax
#=> [13.99, 33.41]
or
arr.map { |s| s[/\d+\.\d+$/].to_f }.minmax
#=> [13.99, 33.41]
If you want the associated records:
arr.minmax_by { |s| s.split(',').last.to_f }
=> ["321,cap,13.99", "222,shoes,33.41"]
With CSV
If you wish to use CSV to read the file into an array:
arr = [["123", "hat", "19.99"],
["321", "cap", "13.99"],
["222", "shoes", "33.41"],
["255", "shirt", "19.95"]]
then
arr.map(&:last).minmax
# => ["13.99", "33.41"]
or
arr.minmax_by(&:last)
#=> [["321", "cap", "13.99"],
# ["222", "shoes", "33.41"]]
if you want the records. Note that in the CSV examples I didn't convert the last field to a float, assuming that all records have two decimal digits.

Answer 2

You should use the built-in CSV class as such:
require 'CSV'
data = CSV.read("text.txt")
data.sort!{ |row1, row2| row1[2].to_f <=> row2[2].to_f }
least_expensive = data.first
most_expensive = data.last
The Array#sort! method modifies data in place, so it is sorted based on the condition in the block for later usage. As you can see, the block sorts based on the values in each row at index 2 - in your case, the prices. Incidentally, you don't need to convert these values to floats - strings will sort the same way. Using to_f stops working if you have leading non-digit characters (eg, $), so you might find it better just keep the values as strings during your sort.
Then you can grab the most and least expensive, or the 5 most expensive, or whatever, at your leisure.