Ruby script for calculating your app's retention curve: http://jfeldstein.com/?p=59

retention.csv

require 'mysql2'
require 'date'
require 'csv'

# Init values
results = []
(1..48).each do |i|
  results[i] = {active_count:0, total_count: 0}
end

# Roll through raw data
lifes = CSV.read("./lifelengths.csv")
(1..48).each do |weeks|
  long_enoughs = lifes.select {|l| l[4].to_i > weeks}
  results[weeks][:total_count] = long_enoughs.length
  results[weeks][:active_count] = (long_enoughs.select {|l| l[3].to_i > weeks}).length
end

puts results[1].keys.unshift('week').join(',')
(1..48).each do |i|
  puts results[i].values.unshift(i).join(',')
end