Find the sum of an array with mixed data types

sum_of_array.rb

def iterative_sum(array)
  array.map{|e| is_num?(e) ? e : string_value(e)}.inject(:+)
end

def recursive_sum(array, sum)
  return sum if array.empty?
  sum += is_num?(array[0]) ? array.shift : string_value(array.shift)
  recursive_sum(array, sum)
end

def string_value(string)
  string_values = {"a" => 1,"b" => 2,"c" => 3,"d" => 4,"e" => 5,"f" => 6,"g" => 7,"h" => 8,"i" => 9,"j" => 10,"k" => 11,"l" => 12,"m" => 13,"n" => 14,"o" => 15,"p" => 16,"q" => 17,"r" => 18,"s" => 19,"t" => 20,"u" => 21,"v" => 22,"w" => 23,"x" => 24,"y" => 25,"z" => 26,"A" => 27,"B" => 28,"C" => 29,"D" => 30,"E" => 31,"F" => 32,"G" => 33,"H" => 34,"I" => 35,"J" => 36,"K" => 37,"L" => 38,"M" => 39,"N" => 40,"O" => 41,"P" => 42,"Q" => 43,"R" => 44,"S" => 45,"T" => 46,"U" => 47,"V" => 48,"W" => 49,"X" => 50,"Y" => 51,"Z" => 52,}
  string.split('').map { |e| string_values[e].to_i }.inject(:+)
end

def run(expected, array, sum=0)
  puts "-- Iterative --"
  answer = iterative_sum(array)
  puts expected == answer ? "Success!\n> expected: #{expected}, got: #{answer}" : "Failure!\n> expected: #{expected}, got: #{answer}"
  puts "\n-- Recursive --"
  answer = recursive_sum(array, sum)
  puts expected == answer ? "Success!\n> expected: #{expected}, got: #{answer}" : "Failure!\n> expected: #{expected}, got: #{answer}"
end

def is_num?(e)
  e.to_f == e
end

value_array = [1, 'all', 4, 53, 'Cats', 24, 'Bilbo Swaggins', 12, 74, 'Wowwie', 23, 60, 13, 46, 'That is amazing']
expected = 893
run(expected, value_array)