如何在Ruby中将数组数组从string转换为float？

Question

以下代码将字符串数组转换为浮点数组:

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

为什么以下返回一个字符串数组而不是浮点数？

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,有更好的方法吗？

Answer 1

因为你打电话each的b,而不是collect,你最终会回到原来的数组,而不是一个新创建的数组.这是正确的代码(我更喜欢收集地图,但这只是我):

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