Ruby 在组中使用正则表达式

我有以下数据：

data = [["/","201408","41"],["/","201409","35"],["/","201410","59"],["/","201411","50"],["/","201412","79"],["/","201501","97"],["/","201502","85"],["/","201503","518"],["/","201504","251"],["/","201505","748"],["/","201506","916"],["/","201507","1008"],["/","201508","449"],["/","201509","235"],["/","201510","195"],["/","201511","229"],["/","201512","202"],["/","201601","142"],["/","201602","134"],["/","201603","17"]]

我想按年份对它们进行分组，但我不知道如何在

groupby

中使用正则表达式。我应该是这样的：

grouped = data.group_by { |row| row[1] }

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但是接下来呢？行[1]字符串是YYYYMM

为什么需要正则表达式？这不是你要找的吗

data.group_by { |d| d[1][0..3] }

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我更喜欢幻觉的答案，但如果您仍然想使用正则表达式：

data.group_按{行{行[1]。匹配（/^（\d{4}）/）。捕获[0]}

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不是很干净，但它可以工作。

行[1]字符串是YYYYMMWrite，所以在问题中。