Issue with troubleshooting an error I am getting - ruby

Question

This is the code I am trying to run which counts the frequency of chars in the array passed to it, and this is the error I am getting frequency_string': undefined methodeach' for "a":String (NoMethodError). I'm not entirely sure what is wrong because this is code that should work and was given to me. Very new to Ruby, and have spent hours trying to solve this on my own. Will take any help I can get.
def frequency_string(chars)
frequencies = {}
result = ""
chars.each do |char|
if frequencies.has_key? char then
frequencies = 1
else
frequencies[char] += 1
end
end
frequencies.each do |char, freq|
result << char << freq
end
return result
end
data1 = ['a', 'b', 'c', 'c', 'd', 'a', '#', 'b', '#', 'a']
puts "Data 1: " + data1.join(' ')
puts
puts frequency_string(data1)

Answer 1

You have two problems:
the line frequencies = 1 should be frequencies[char] = 1. As it stands, you are converting a hash to the number 1.
you have frequency[char] = 1 and frequency[char] = 1 reversed.
Here is your corrected code:
def frequency_string(chars)
frequencies = {}
result = ""
chars.each do |char|
if frequencies.has_key? char then
frequencies[char] += 1
else
frequencies[char] = 1
end
end
frequencies.each do |char, freq|
result << char << freq.to_s
end
result
end
data1 = ['a', 'b', 'c', 'c', 'd', 'a', '#', 'b', '#', 'a']
puts "Data 1: " + data1.join(' ')
puts
puts frequency_string(data1)
#=> a3b2c2d1#2
As you gain experience with Ruby you will find that the language allows you to write operations such as this one with very little code. Here's one way:
def frequency_string(chars)
chars.each_with_object({}) { |char,hash|
hash[char] = (hash[char] ||= 0) + 1 }.to_a.flatten.join
end
puts frequency_string(data1)
#=> a3b2c2d1#2
This may look complex, but it won't be long before you find this to be more natural and straightforward than what you have written. You don't have to worry about this now; I just wanted to give you a taste of what you can look forward to.

Answer 2

chars.each do |char|
if frequencies.has_key? char then
frequencies = 1
else
frequencies[char] += 1
end
end
should be:
chars.each do |char|
if frequencies.has_key? char
frequencies[char] += 1
else
frequencies[char] = 1
end
end
or
chars.each { |char| frequencies.has_key?(char) ? frequencies[char] += 1 : frequencies[char] = 1 }
You also can make it like this:
group_by usage
irb(main):038:0> data1.group_by { |e| e }
=> {"a"=>["a", "a", "a"], "b"=>["b", "b"], "c"=>["c", "c"], "d"=>["d"], "#"=>["#", "#"]}
irb(main):041:0> data1.group_by { |e| data1.count(e) }
=> {3=>["a", "a", "a"], 2=>["b", "c", "c", "#", "b", "#"], 1=>["d"]} # it can be an optional if it can meet your demands
after improvement：
irb(main):053:0> result = ''
=> ""
irb(main):054:0> data1.group_by { |e| e }.each { |e| result += e[0] + e[1].count.to_s }
=> {"a"=>["a", "a", "a"], "b"=>["b", "b"], "c"=>["c", "c"], "d"=>["d"], "#"=>["#", "#"]}
irb(main):055:0> result
=> "a3b2c2d1#2"
or use inject
irb(main):040:0> data1.group_by { |e| e }.inject('') {|r, e| r + e[0] + e[1].count.to_s}
=> "a3b2c2d1#2"