R中的数据变换：子集和排列不均匀长度的向量

I am sorry I could not make a more specific title. I am trying to wean myself off of spreadsheets for the more difficult tasks and this one is giving me particular trouble - I can do it in Excel but I don't really know how to begin in R. It is somewhat hard to describe. I imagine a mix of techniques could be involved here so I hope this is of use to others. I am sorry I could not make a more specific tit