I'm currently working with a .csv file in ruby and I'm trying to figure out how to count the number of items that are over 60 in the file.
I've imported the csv file into a hash and counted the total number of items, but I want to know how to count the number of items over 60 now.
This is an example of what I'm looking for
csv.csv:
55, 56
60, 61
63, 9
3, 62
My code so far:
myhash=[]
myhash1=[]
total=0
count=0
file=File.open('csv.csv',"r")
???
puts count
Expected output: 4
There are multiple ways to solve this. Here's one approach that does the whole operation in one go, without even looping through each line:
File
.read('csv.csv') # Read the file into a ruby String
.split(/,|\n/) # Convert into an Array of each string (splitting on commas OR newlines) (e.g. ['55', '56', '60', ... ])
.map(&:to_i) # Convert into an Array of each integer (e.g. [55, 56, 60, ... ])
.count { |n| n >= 60 }
Here's a similar approach, that instead loops through each line and adds the count to a variable. Using foreach like this is especially better if you have a very large file - as you won't be loading it all into memory at once:
total = 0
File.foreach('csv.csv') do |line|
total += line.split(',').count {|n| n.to_i >= 60 }
end
And here's another approach that actually uses ruby's CSV library, so you don't need to explicitly split on the commas:
require 'csv'
total = 0
CSV.foreach('csv.csv') do |row|
total += row.count {|n| n.to_i >= 60 }
end
While I usually caution against using naïve means to deal with CSV data, if indeed your CSV file is all numbers, then I think using the CSV module is overkill. You can use File.foreach to iterate over the file's lines and String#scan to iterate over the numbers in the file.
n = 0
File.foreach("csv.csv") do |line|
line.scan(/\d+/) {|s| num += 1 if s.to_i >= 60 }
end
p n # => 4
This method has the benefit of not reading the entire file into memory at once, nor creating large intermediate arrays.
You can see it (almost) in action on repl.it: https://repl.it/IY5X (It's different only because you can't read from files on repl.it.)
The shortest way I know of to do this is:
File.read('foo.csv').scan(/\d+/).select { |d| d.to_i > 60 ).size
Don't forget about Enumerable#count
Good point:
DATA.read.scan(/\d+/).count { |s| s.to_i > 60 } # => 3
The downside to these is that they're not scalable. See "Why is "slurping" a file not a good practice?" for more information.
If the values are all treated equally:
require 'csv'
CSV.read('input.csv').flatten.map(&:to_i).count { |i| i >= 60 }
# => 4
