如何將字符串數組的數組轉換爲Ruby中的浮點數？

Question

下面的代碼字符串數組轉換成float數組：

a = ["4", "5.5", "6"] 
a.collect do |value| 
    value.to_f 
end 
=> [4.0, 5.5, 6.0] 

爲什麼下面的返回一個字符串，而不是float數組？

b = [ ["0.0034", "-0.0244", "0.0213", "-0.099"], 
     ["0.0947", "-0.1231", "-0.1363", "0.0501"], 
     ["-0.0368", "-0.1769", "-0.0327", "-0.113"], 
     ["0.0936", "-0.0987", "-0.0971", "0.1156"], 
     ["0.0029", "-0.1109", "-0.1226", "-0.0133"] ] 

b.each do |row| 
    row.collect do |value| 
     value.to_f 
    end 
end 
=> [["0.0034", "-0.0244", "0.0213", "-0.099"], ["0.0947", "-0.1231", "-0.1363", "0.0501"], ["-0.0368", "-0.1769", "-0.0327", "-0.113"], ["0.0936", "-0.0987", "-0.0971", "0.1156"], ["0.0029", "-0.1109", "-0.1226", "-0.0133"]] 

另外，有沒有更好的方法來做到這一點？

Answer 1

由於您在b而不是collect上致電each，您最終將返回原始數組而不是新創建的數組。下面是正確的代碼（我喜歡地圖收集，但是這只是我）：

b.map{ |arr| arr.map{ |v| v.to_f } }