Basic text analyzer from Peter Cooper's Book; Beginning Ruby

Analyze.rb

stopwords = %w{ the a by on for of are with just but and to the my I has some in}
lines = File.readlines("text.txt")
line_count = lines.size
text = lines.join

#Count the Characters
character_count = text.length
character_count_nospaces = text.gsub(/\s+/, '').length

#Count the words, sentences & paragraphs
word_count = text.split.length
sentence_count = text.split(/\.|\?|!/).length
paragraph_count = text.split(/\n\n/).length

# Make a list of words in the text that are not stop words, 
# count them, and work out the percentage of non stop words
# against all words
all_words = text.scan(/\w+/)
good_words = all_words.select{ |word| !stopwords.include?(word) }
good_percentage = ((good_words.length.to_f / all_words.length.to_f) * 100).to_i

# Summarize the text by cherry picking some words to use
sentences = text.gsub(/\s+/, ' ').strip.split(/\.|\?|!/)
sentences_sorted = sentences.sort_by { |sentence| sentence.length }
one_third = sentences_sorted.length / 3
ideal_sentences = sentences_sorted.slice(one_third, one_third + 1)
ideal_sentences = ideal_sentences.select { |sentence| sentence =~ /is|are/ }

# This is for giving users feedback. In line 2, I wanted to make it File.readlines(ARGV[0])
# so users could let this read any text file they may have save onto their computer from the command line/terminal, but when
# I tried doing that, it returned an error; "can't convert nil into string". I will try to 
# fix it. 
puts "#{line_count} lines"
puts "#{character_count} Characters"
puts "#{character_count_nospaces} Characters excluding spaces"
puts "#{word_count} words"
puts "#{sentence_count} sentences"
puts "#{paragraph_count} paragraphs"
puts "#{sentence_count / paragraph_count} sentences per paragraph (average)"
puts "#{word_count / sentence_count} words per sentence (average)"
puts "#{good_percentage}% of words are non fluff words"
puts "Summary:\n\n" + ideal_sentences.join(". ")
puts "End of analysis"